Everyone has such great advice! Like any relationship, I think a lot of folks experience lulls in things they enjoy and I'm sure you'll find the passion again. Can you use your bike to commute (work, store, etc. -- or pubs as other have suggested)? Sometimes having a destination makes it more doable when you don't think you feel like riding. You can take your time and just enjoy being outside and getting that fresh air pumping through your lungs.

Just as a side note, think about having your thyroid levels checked and other blood work. Before I found out I had hypothyroidism, I was loosing interest in doing things on top of being tired. It was such a subtle change over time that I thought it was because I wasn't taking care of myself properly (not eating right, not exercising enough, bla bla bla), even though I knew better.

Good luck and keep us posted.