Adam, you have to learn to move on. If you don't feel like dating now then wait until you are ready. Yes, dating is exhausting but when you look like a fitness model it must be much easier than for someone who is not. You can't tell me women don't approach you alot.
Remember she has to deal with seeing you too. You don't think this is hard for her too? How is she dealing with seeing you at work? Maybe you can learn something from her if she adjusting better than you. I know your hurting because she was the one who ended it instead of you. That can be a slap in the face especially when you thought your love was solid enough to get thru anything. However, you see it wasn't. That is your cue to realize you have to find something more solid with both people feeling the same way. Life is never easy for anyone when it comes to relationships. Look at divorce rates. They are at an all time high. Do ever question why is that? For now do what you love to do and go to the gym and make it a project to help some skinny guy get into shape like you. Keep yourself active on things you like to do and when you are ready to date again then do it. If not, you will lose out like I do because I hate the process of dating too. Don't be like me. It shows I take the easy way out.