Is NOBODY wrong in the post ? POST : Couldn't find a better way to phrase it.

I'm actually having this issue with two of my friends, but the one that bothers me more is the one with my best friend, so I'll go with that.

I'll start by acknowledging my blame: I find it hard to say "No" when people ask for my help and I get upset when they don't show me the gratitude I think I deserve for helping them.

My best friend and I have a great friendship, we used to hang out a lot, either just the two of us, or in a group of friends, or just me, him and his girlfriend. We used to see each other at least every two weeks, but we have the kind of friendship where we could not see each other for months and still be best friends when we meet. 

A month and a half ago, he was in the middle of his exams, while I had finished mine (we go to the same university), so, naturally, I wanted to relax for a few days, use my days off from work to get some rest and visit my family. However, he asked me to help him study for his remaining exams and, reluctantly, I said I'd help him. I know I should have refused if I really didn't want to, but I couldn't bring myself to tell him no, so I spent my free time studying together with him for his exams. This went on for three days, admittedly not a long period of time, and he knew I had put aside my plans in order to help him.

Aaand that's the last time I've seen my friend. Ever since, I've initiated conversations with him, hoping that we'd hang out, but he was always dismissive or not answering my texts. In this time, he went out only with his girlfriend and her friends, never with our group of friends. Now, don't get me wrong, he has always spent more time with his girlfriend than us and that never bothered me, I would never intrude on his relationship. Plus, me and his girlfriend get on really well, so I'm not being petty.

Recently, he has been trying to reconnect and this time I didn't feel like hanging out with him anymore because I still feel that I was discarded when no longer needed, so I was dismissive when texting him. He just sent me a message asking me if I'm upset with him and I thought I should ask your opinions before answering.

P.S. I know I said I'd only talk about the situation with my best friend, but now I think I should mention my other friend for a better understanding of my almost pathological inability to say no. The other friend is my roommate, he is one year younger than me and goes to the same university as I, and he always asks me for help on exams and homework. He always showed gratitude for that, so that's not the issue. My problem is that, during the summer vacation, three months long, he always came up with an excuse to not hang out. I brought it up to him last night and he seemed to realize I was right, but was dismissive of the conversation and just kept saying I wasn't right, thinking I was joking even though I insisted I was serious. This just made me more upset.

Sorry for the long text, thanks for reading!