my boyfriend is always so critica

whenever I go to the gym with my boyfriend I get so irritated. he's so rude to me whenever we work out together and acts like he's an expert and whatever I say doesn't matter. when we were just doing our abs apparently my legs where going too far down and too far up, and he's like "oh my god I can't believe you can't do these". I obviously can just not perfect. I started doing them again and he just said oh my god so I stopped and said "there's a difference between being critically rude and being critically helpful". And when I asked him to be nicer he just said I need to shut up & listen. It's not like I'm arguing with what he's saying, I'm just not understanding what I'm doing wrong.  And he helped me do them "correctly", then said "only took one fuck up, I expected it to be at least four". And I got up and said ok I'm gonna go tan now. & "some comments you say just aren't necessary". I said that because I was sick of him being so rude to me. And then he said "don't bitch anymore about your abs". Understandable, but I can't sit there with someone who is being so rude to me. It ruins my entire workout. I always question the entire relationship when we go to the gym because he is always so rude. Yeah, I'm not a gym expert but I did used to be pretty fit and workout even more than he did. And he just says "stop asking questions. Who knows more about the gym, me or you? Me." Any time I Express to him these frustrations he just tells me I "talk back" & I don't listen. Basically me asking questions or ask how I'm doing something wrong isn't ok and I should just shut my mouth and listen. It's never ending. I can't tell him why he's upsetting me without him putting the blame on me. What should I do?