Pregnancy strain on marriage/sex

Anyone else feel like since being pregnant that it's put a strain on your relationship. I feel like every argument that's sex related has to do with because something is uncomfortable for me. Since day one I told him sex may change. Some days I may not want it and he seemed okay with that. I was a horn dog first trimester, tapered off the second and picked up towards the end and now that I'm almost 8.5mo it comes and goes...and I try my hardest but I honestly can't keep up with the type of sex we've had our entire marriage because I'm a good 40lbs heavier. I get out of breathe quick and certain positions don't work for me. "Last time I get you pregnant" and it makes me feel shitty every time like I try try sooooo hard I know he's got needs and I try my best to keep up with them. Then when I get hurt because of the statement he gets pissy saying how he can't say anything...how else am I suppose to feel? It's frustrating and I don't know how much I can take before I explode.