Don't find dp attractive, find someone at work attractive.

[Feelinglostsong]

A few weeks ago I had a miscarriage. I have been with dp for 7 years and I love him. The miscarriage was devastating but now I've gone from that to not wanting any kids just now for a few reasons.
I am losing weight and starting to look and feel good. Dp is very overweight and I'm finding sex between us uncomfortable and I'm struggling to find him attractive. I feel sick with myself for this because he is the nicest man I've ever met....but I'm not enjoying sex at all.
I have a huge crush on a married man at work which I think is mutual. We haven't spoke about it and don't work together so don't talk much...no chance of anything happening and I don't think we would allow anything to anyway. He is always in my head and I think he's gorgeous.
I love dp, we have a mortgage together and my dd loves him very very much. I don't want to split up because as I say I love him....i am just struggling with sex and attraction.
What do I do?

It sounds like you still want kids but because the embryo made from you and your partner didn't work out, you're looking to find another mate you could make a viable embryo with.

I don't know if scientificly that's the case or if it's been a big wake up call that this isn't really what I want. I just don't know anymore.

It's normal to have lulls in attraction in long term relationships. It's also normal to fancy other people. Stop fretting about it.

You need to work on your partner, get him on board with healthy eating and some exercise and focus on improving things at home.

You're playing with fire entertaining the idea of this colleague (trust me, I've been there).

The thoughts about him are almost certainly affecting the way you see your dp. You will be subconsciously comparing them. This won't help your relationship.

OP - first off - stop having duty sex.
Nothing good will come or if it - you’ll only resent him more and more.
If him being overweight - is part of the diminishing attraction - you need to tell him. In a gentle way - obviously, but tell him.
Or - somehow suggest a change of diet...

However - if it doesn’t change and improve over time - sadly - I don’t think the relationship has a future.
Unless a sexless partnership is what both of you will be OK with