Thanks for all your responses - some good points.
At the heart of it I suppose the issue is lack of sexual attraction. Kissing and cuddling are great, but I hardly ever (almost never) feel like dragging him to bed. I still find him attractive, but it's like a lack of 'manly physical presence' thing. We've been together a few years at this point, and I'm struggling to figure out:
a. If this is just pretty normal for long term relationships. The butterflies don't last forever (for me they were pretty strong for the first 6 months or so) and beyond that it's about a more content feeling, and the attraction takes work. I do still look forward to seeing him.
b. Everything else in our relationship is so positive, it'll be ok to carry on like this (forever?), or if I'll always feel like/worry there might be something missing
c. It's just a fear of commitment, of this being 'it' thing - I've created a mental block because the next step is just rather scary. How do you know when you're making the right choice? Why do I feel apprehensive a lot of the time, instead of just in love and excited?
d. If I were to leave, what the chances of finding such a good relationship again are. It's easy and comfortable and I feel loved and safe. Life without him would just be sad, hard and lonely.
e. I just need some serious therapy. These are personal insecurities that I'm somehow projecting onto our relationship
There have been men (in the past) who I have been massively attracted to, particularly physically. Things have never got to this stage with any of them - either the relationship has been short lived and ended badly, or they have not shown the same interest in me.
I don't want to throw away something great just because I might have unrealistic expectations and put unnecessary pressure on things. I also don't want to rush into any stupid decisions, but know that at some point I'm going to have to commit one way or the other.
Thoughts/advice/similar experiences? Apologies this is all rather self indulgent and I realise that there are people posting in this forum with much more critical issues. Nevertheless, if you want to comment, I'd appreciate any feedback.