We broke up because I felt strangled and that I wanted to build myself.
Can a person build himself while he is in a relationship, or if I feel I'm not a whole person I need to be alone in order to build myself up? Can I just change a few things about the relationship - for example not give up trips because I'm worried it will harm my relationship (which I did) not give up things that are important to me just because they may harm the relationship? Will that be enough for me to not feel strangled?

I love him very very much.

If the relationship is good you grow together, you both have the space you need to grow, and the encouragement to grow. If he's not giving that to you, it's not a good relationship.

Of course you can change the things you stated, you have a right to live your own life, being in a relationship doesn't change that. The only thing you can't change is who he is, and if that's what you're wanting to change, you're fighting a losing battle. Either love him for who he is, or find someone that is who you want them to be.

Only you can decide what to do, but it sounds like you're very insecure in this relationship. I have to wonder if that's just the way you are, or the way you are because of him.