How do i get back into the gym?

I was forced to stop playing college football and I cannot find myself to be motivated to go to the gym and get a consistent workout regimen. I know what I'm doing when I'm there but its getting there that's the problem. I think its mainly because since 8th grade I was motivated to get better for football so I was always the first one in and last one out every day. But now I have been on and off going to the gym and I can't get back to that athlete body I once had. I don't know what to do and I don't want to get fat and have high blood pressure and all that bull. Thanks for your help in advance.