TTC for two years!!!

My husband weighs 248lbs. He is an active person. He does labor work and also play volley ball once a week. I weigh 126lbs. We are TTC for our first for more than two years. He gets really sweaty and tired after having sex. He has hard time being erect for more than a min or two. BD every other day is so difficult for us. His sex drive is lower than mine. He can go without it for a month. I can do every other day but for him he is always tired! We have done one IUI but it didn't work. We are going to TTC every other day. Any suggestions?