My boyfriend has been very short with me lately and gets aggravated whenever I express my emotions?

I'm a VERY emotional person, cause of this I tend to be very hard on myself and I can get very upset even over small things. At first, he was generally sweet/caring to me when I was sad. I've noticed lately, he's become more hostile with me whenever I bring up I'm feeling upset.

I get why considering I do it often, but I've really been trying to make sure that I'm not as sensitive so when I say how I'm feeling for the first time over the span of a few days, which is groundbreaking for me, I get short/annoyed replies. I tell him it'll be okay and just to let me cool off and he proceeds to admit he gets angry whenever I do seem upset, and becomes hostile

I feel he has good intentions but it hurts when I seem to only anger him. I'm really trying to change the way I act so that this won't bother him anymore, but I'm lost. He's not upset nearly as often, he's usually laid back but his only issue is how quick he gets mad - but when he's upset, I ALWAYS give my 100% to make sure that he's okay.

I feel I do the best I can as a girlfriend, doing everything I can to make him happy but I feel I can't. At the start, we didn't have issues like this. It was so happy, then after that, I dunno what happened. Issues occurred more often, and I began to show him my more emotional side.

Why is it whenever he's upset, I write paragraphs explaining how much I love him while I get BS? Why is it that whenever I express negative emotions, I feel I get punished for it? I know he's bad at expressing himself, but I just feel like I pull all of the weight. Whenever he's upset, he also takes anger out on me.

We both know we want to keep this relationship but we're both scared of where it's going. I'm sick of feeling to blame. We've discussed many times and we've both said we were going to try to make sure that problems become less frequent but the effort seems one sided. I'm sorry for ranting but this has been going on for so long. I just really need help. I love him but I feel so helpless.
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TL;DR- boyfriend gets mad when I get upset and responds with hostility upon me being upset, admits to gradually being more annoyed by my overly sensitive behavior over time. I've tried to change myself for him and stop taking everything to the heart, problems seem to keep occurring. I feel that attempts to stop all these relationship issues are very one-sided. After countless discussion about relationship conflicts, problems don't seem to be getting better. I feel I'm the only one pulling weight.
My boyfriend has been very short with me lately and gets aggravated whenever I express my emotions?
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