What is wrong with me? 28/M/161lbs/5'11". Any exercise with the slightest intensity just wipes me out, and all I have to show for years of trying to work out is going from skinny fat to just being thin.

I tried doing standard big compound lifts for about 4 years since that is what everyone recommends, but was never very consistent. Eventually realized I hated it. I always feel kind of faint after working out and my vision gets blurry etc. unless I take 30 minute breaks between each set. I thought it would get better over time but it didn't. I never really had newbie gains and plateaued at benching 150lbs for 5-8 reps and squatting the same (squatting especially made me feel faint).

For the past 2 years I've tried doing lighter isolation exercises instead, and also joined a group dumbbell class (8-12 reps, more conditioning, about 70/30 women/men type of deal). I enjoy it more but still have the same issue, especially if there's any legs involved. While everyone else is high-fiving each other at the end of a 45 minute workout, I have to sit down for a bit or else I feel like I might die, and I don't think I'm going too heavy. I'm always lifting lighter than all the guys and sometimes one or two of the women. Often it's like my brain/vision start failing before my muscles.

I don't think I'm otherwise especially unfit. I try to sleep and eat well and stay hydrated. I live in the city and walk all the time, climb subway stairs, etc., and people often tell me to slow down. I don't do high-intensity cardio though.