Disenchanted

So today I found out something...something I didn't want to know but already sort of knew. I wish I could be more specific but now that people actually read my blog I can't.
This thing tears me up inside, I don't know if anyone would understand why but it hurts. I know he loves me but if he loves me why does he need that? Aren't I good enough? Apparently not as good as he's made me out to be. I don't want to be this upset about it because I shouldn't and I know if I make a big to do about it he'll never be able to trust me with anything. It makes me feel like I'm not doing enough so he's got to go and get it somewhere else. Maybe if he's going to that then I don't need to do anything because he's got all he needs with it. I know this sounds stupid but I feel like I've been cheated on or something. Wouldn't you in my situation.
And somehow in all this I can't help but feel guilty and angry at myself.
Guilty because I'm obviously not doing good enough and angry at myself for letting this upset because I really have no right whatsoever to be upset.
Sometimes I think life would be so much more easy if I just didn't care. I want to lash out at him and scream at him because it hurts me so much but at the same time I want to shut my mouth and keep to myself because it makes him happy. Ever since I've met him I just don't know what I want anymore.
I don't know what I hate I don't know what I love, I'm just so confused about everything and it's all overwhelming because it's like one huge mess in my mind that is impossible to sort. I need psychiatric help. I'm probably mentally crazy.
That's one of my fears. I fear that I have an undiagnosed mental disease.
It's just so hard for me to really think about things. It's all just jumbled up into emotions.
I'm so angry, and I don't know if I'm angry at him or me I'm just angry. I'm angry at us both! I'm just I don't know! I'm sad and hurt and disappointed and I wish he had never done that but I wish I'd never known, but it would be so much better if he just hadn't done that because I can't tell him not to do it because then I'm not being a very good girlfriend.
I just want him to know that I love him and if that's what he chooses I can live with that just as he's lived with me and I don't want him to stop doing ANYTHING he enjoys just for the sake of my happiness. I especially don't want him to lie to me under any circumstances. I'd rather be hurt by the truth than be happy and have him lie to me. I'm so confused. Can anyone help me?