I am in a relationship with an older man and I am really worried that I am not good enough for him. I see him look at other people and I feel like he would rather look at them than me. He tells me that how I feel is not the case and even though I believe him I can't help the way I feel. I would like to overcome my insecurities, but I don't know how. If you have any advice or opinions, please let me know. Thanks.

There is no magic answer to having more self worth, you have to get to the point where you feel he is lucky to have you. ( or close to that)
It may well require counseling to get to the root issues of why you feel the way you do.

I have felt that way, maybe strays from way back, not having a lot of friends (but I have some really good ones). Being made fun of in school, just little things that are not great for self esteem. I would reallly say you are great for him, or he wouldn't be with you. I have had insecurity issues and wanted to feel wanted. Looking back, it was a bad thing in my head, that little part that thinks completely unrelationally and takes over everything else. Do not let it control you. I feel so good about myself just because I have been trying to see what I need to work on in my life and also what I am great at.

Love yourself enough to see the value you bring in the life of another, and leave the doubts at the door. If you need guidance to understand how to love yourself, there is no shame in getting it. It comes down to enjoying the good in life and dealing with the rest. Don't take it personally we all have those days.