I have read several other posts similar to this, but I want to get opinions on my own specific situation.
I am 21 and my boyfriend is 22. We have been dating for 2 years and are quite serious. We broke up for a month this past summer because he "didn't know what he wanted", but he later came back to me, and said that it had all been sparked because we were about to graduate college and he was terrified because he cared about me so much and thought that I might be the one, but was afraid of settling down so young like so many of our friends have... We both have so many more things we want to do and we hasn't previously discussed marriage eventually, so he didn't know that I was also scared.
Anyway, for our entire relationship, his sex drive has been through the roof. He has always been aggressive and touchy feely and all over me. He still is this way in most ways. He still holds me at night when we sleepover at each others houses, he still holds my hand in public and stops me in the middle of campus to kiss me in front of everyone, and always has his hands on me. He compliments me all the time. In the past, sex was usually an extension of this behavior-- us making out in a parking lot after dinner might lead to us having sex in the back of his car... Him spooning me at night would lead to it without a doubt. But I never thought we were boring. We played around constantly, had sex in random places, played dress up, took turns initiating it, made videos (just for us, we deleted them after!) and I even recently started to have (and really enjoy) anal sex with him. We had sex at least once a day, if not more. Once we had sex 11 times in one lazy Saturday. The only thing ever "off" about our sex is that he often comes very quickly.. Sometimes before I can, but always makes up for it. But I've never ever made him feel bad about it. He still makes me come in some way no matter what and I enjoy how we mix it up.
I geuinely love our sex. And I love him. And I love the sex partially because I love feeling wanted and close to him.
I guess I just never thought that sex would be a problem with us. I'm very attracted to him and I think he still is to me by his behavior otherwise, but we've only had sex twice in the past three weeks. I know a lot of older couples might laugh this off, but we spoke about it tonight and he agrees that something is wrong but he doesn't know what.
He said that he is more in love with me than he has ever been, but that for some reason he just hasn't been as sexually motivated in the past few weeks. He does work out a lot and thinks it may have something To do with the supplements he takes/his fluctuating testosterone levels, but shouldn't extra testosterone make him MORE horny?
I got him open and talking about it and he says he doesn't feel like even watching porn when he is alone.. Which he doesn't do much, but does occasionally when we aren't together for a few days at a time. He said that he is used to thinking about sex 23 hours a day and now doesn't really even when he should be (I.e. with me).. I told him that I understood but that it was making me so insecure and he held me and reassured me and said that it was making him really insecure too because he wanted to be able to please me. I just am really panicking because deep down I am afraid that he has lost interest in ME, not in sex. I thought that talking it out would reassure me, but I'm afraid he wouldn't want to hurt my feelings if it really was me. I just am scared because for two years I have thought about wanting to marry him and now I am afraid ill never get out sex life back to normal... Which would be every other day at least, with both of us engaged in it and excited about it, not just going through the motions. If this is happening now, what would happen after 10 years of marriage?
I know many people may say that he could have someone on the side-- which I suppose anything is possible-- but I really really don't believe that this is the case. We are very open with each other and are together very often. While most of my girl friends have caught their bf's texting or flirting with other girls, he's never done anything to betray my trust in the slightest. He's always made me feel so loved-- and still does, besides this.. And I wish that "this" wasn't such a big deal to me, but it is for some reason.
What should I even do? We are open to talking about it, but have no idea where to begin..

Sorry some older couples still have sex several times a week, I average about 5 or 6, but then I work 18 hours a week and my wife only works about 4. We have no real worries about life and almost no stress, every day is like a holiday almost. We get 18 weeks vacation a year 3 periods of 6 weeks, plus lots of other holidays.

But real people in real life, at 22, have jobs, have money stress, and that kills a sex drive.
And he needs to talk to a doctor about hormones, if you mess with them and get things out of balance, it can have serious effects, even long term.

But for a working couple, that several times a day falls to about 2 or 3 a week and sometimes less because of schedule, After a baby it often falls to less, since both people are often dead tired and sleeping is more important than sex.

Things like 11 times a day, merely means that you both need a life and other activities and not base a relationship on sex. And that seems to be part of the issue, that without sex, there is not enough love and partnership to keep it going.
What if he had a medical issue and could never have sex again ? Are you gone or are you there for him,
That will tell if you love him, or just want to be loved with him