Obviously I am unfamiliar with your personal situation, but a friend experienced a similar thing in her relationship:

She got diagnosed with vaginismus, which is basically involuntary muscle spasm around the vagina, which makes penetration painful to impossible.

I believe what helped her (alongside talking therapy), was using a dialator set/kit (basically very soft, untextured dildos that start very small (a few mm, and go up to about the size of a penis), which are explicitly made to help with Vaginismus.

She initially was treating more it a bit more like physio than intimacy; according to her BF, she didn’t realise you are supposed to effectively masturbate with them, apparently she would just lay there with one in and then wonder why there wasn’t much improvement, her therapist corrected her regarding this.

I also found out that her BF didn’t like sucking/playing with her nipples (also correctly guessed he was bottle fed from that, haha). Told him to stop being an idiot and engage with that bit and it’s no longer an issue for them…

Other suggestions that have a much more immediate impact, but are less conventional and do carry some risks so I’ll mention it for the sake of covering all bases;

Poppers as in Alkyl Nitrites, the things that are popular in the gay clubbing scene, help massively with this by reducing the constriction of smooth muscles in the body/abdomin… (Meaning it loosens the muscles in the wall of your vagina, and also your butt), it also has secondary affects on blood pressure and makes you feel slightly drunk and mild euphoric