:/ Insomnia :/

Lately, I've been having trouble sleeping mostly due to the shaky situation between my SO and I. I've been smoking three times as often and been eating a lot less, I've lost 5kg in two weeks. It may be due to the fact that I noticed that he lost interest in me after three years together, he watches videos like how to pick up hot chicks on youtube, signs up for dating sites, watches porn more often and he's very cold towards me these days. I've written about this before but I'm having trouble letting him go and the fact that I know I must let him go soon keeps me down and not letting me sleep. What should I do? I was thinking of yoga or hitting the gym more often but my mind is just not there anymore.