I hope you take the time to read this, I really need help.
I broke up with my boyfriend of 3 years on December 10th, we agreed to be best friends. It was mutual, just sick of the relationship stress I guess.
I started hanging out with another guy and our feelings progressed and we still really really like each other, he made me sooo happy and he said he had never met someone that had made him this happy.
Well my ex didn't like this and he knew that we both liked each other. He had brought up the point a few times to me and he said I just never cared about his opinion. He brought it up again last night and he made me choose between him and this guy (that was his friend before this situation)
My ex knew this guy had lied before to get more attention, so he figured that this guy would be bullsh!ting me to get me to like him. I believe everything this new guy says to me and he is one the sweetest guys I've ever met and he deserves to be happy.
So anyway I told my ex that I chose him(my ex) because 3 and half years of going out and being best friends is too much to throw away for a guy I've known well for like 5 months.
This guy I like has told me that he has never had someone that has made him this happy before, and I feel like I am what is keeping him going, I feel that if I tell him we can't hang out anymore I am going to ruin his life right now, its going to be so hard and I will feel like the most horrible person for taking that happiness away from someone, I would also feel bad for not choosing my best friend of 3 years, but he hasn't treated me very well lately, and my girl-friend and my mom think he hasn't been fair, telling me that I can't see this guy while he goes to hang out with girls that have feelings for him(but I can't say it bugs me because it doesn't.. ) I haven't been happy hanging out with my ex, all I can think of is this other guy and how happy he makes me. I think my ex is much stronger to handle if I picked the other guy, this guy I like is very sensitive.
So anyway I'm going to tell this guy I can't see him anymore, but its eating me up inside, I feel so horrible, this is going to hurt him so so much.
[i am in grade 12 right now ,just so you get a sense of how old I am.]

Well, I think this is clearly an issue of your ex still running your life. To be honest, I am not sure you should be friends with someone you have had a romantic relationship with... at least not for awhile. There has to be some kind of emotional detachment, which takes a lot of time, especially after being together 3 1/2 years. I would imagine that any guy you talk to or have romantic feelings for would illicit the same response from your ex, which is why it is important not to have them in your life for awhile. You can be friends and then start a relationship, but it is much harder to be friends after being in a romantic relationship...

I would also steer clear of being in a relationship for awhile... this sounds dangerously close to a rebound. It may also be a good idea, if you choose to get involved with another guy, to make sure it isn't a friend of your ex. That can make for an awkward situation.

You also shouldn't have to choose between people... that is a bit unfair, and your ex, no matter how good of a friend he is/was, doesn't have the right to ask that of you. Your personal life is your business... period.

It's clear that your ex stills has feelings for you or don't want to see you happy. Either way your allowing him come between you and your happiness, don't let him.

If he can't be your friend than you don't netd to be his friends. What is going stop him from interfering with the next guy that comes along.

If your going be friends he is going to have to accept who you date. He can offer his opinions at times but must make sure it isn't base on emotions.

You need to go get this guy and don't let him get away. Otherwise, your going reflect back on this and start thinking of the "what if". It might work it might not but isn't it worth seeing for yourself.

If your ex can't accept it than maybe it's time for some new friends. Live your life because you only have one to live and tomorrow isn't promise.