I think it's great that you want your boyfriend to be healthier. Everyone is correct in saying that you can't force him to do anything, but I think you could encourage him and invite him to work out with you! Make it fun, challenge him, whatever. He helped you, and you could help him - but that's only if he accepts your help.
Also, I agree with everyone else, and I want you to be careful. Always change you for you and not for others. It's great that you're healthy again, and I'm so greatful that you are! I want you to be careful not to be dependent on said boyfriend to help get you through stuff - it is SO important that you know you can run your life on your own, and make your own decisions - I had a bump in the road where I was depressed, anxious, and suicidal, and now that I am pretty much bounced back from that, I realize just how important that is.
HAVE CONFIDENCE IN YOURSELF - YOU'RE WORTH IT!