Why don't I want to have sex anymore?

Okay quick background on me:

23, have a 2 year old and been in a long term relationship and still am...

But for the past few weeks (months?) I just have had 0 sex drive. I'm on the copper IUD so it's nothing hormonal/because of birth control.

I have pretty could self esteem 90% of the time.

Still in love with my boyfriend

Most of the time I'm really tired so I don't want, but then sometimes the thought of it just is like a no for me.

Has anyone gone through this? What should I do to get my sex drive back!?