SO being different!!

When my SO and I got back together everything was going good. We have been back together for almost two months now. It started great, sex was great and everything. When we did have sex it was only for like five minutes. I wouldnt get off or anything. He would just roll over and go to bed. Now for almost a month he hasn't touched me, kissed me like he use to. We use to joke around and play around the house but now he doesn't. I talked to him about it all and all he says its all because he is stressed. I need some some advise.