Partner avoiding sex

Myself and my partner are mid 30s and have been together 10+ years.

We have a 3 year old daughter and I am desperate for baby no.2.

I voiced this to my other half who reluctantly agreed, but since then (3 months now) he has been doing everything to avoid having sex with me.

We have had sex maybe 8 times in total since I mentioned it. And while I'm doing everything I can (taking bbt daily, and using opks) on my high peak fertile days, if I try it on with him, it never happens, he fobs me off as being tired.

I feel like this is building a massive rift between us, but I would do anything to have another baby, and a sibling for my daughter.

I feel like if i sit him down and talk about it, he's going to tell me that actually he doesn't want anymore kids, but then where does that leave me?