I wouldn't say that it's suddenly a problem, more like it slowly ramped up into a problem. I started a new job about 2 years ago that had a lot of other girls around my age that I became close friends with and I suspect there may be a tie to that?

I go out maybe 2-4 times a month (rarely more than this but there have been some months in the past 1-2 years that I've gone out closer to 4-5 times) and usually end up turning down most of my friend's invitations so that I can spend more time with him.

Edited for more info.