Tummy pains and nausea

Hi everyone. I had my third iui on Monday and almost immediately after (with an hour) I began experiencing cramping and nausea that has been there pretty consistently. The nausea gets better every time I eat but as I'm watching my weight I don't want to be constantly eating. The cramping also feels weird and different from my normal period cramps. And I've had a bit of lower back ache. I used letrozole days 3-7 and had an hcg trigger 20 hours before iui (same as with last two iui). I have never experienced any of these feelings with the last two so I am hopeful that means that something is working this time....or am I just looking for something that's not there??  Has anyone experienced this with iui and got bfp???