Help! What’s going on with my body?

I’m between 9-10dpo and since about 4-6dpo I’ve had extreme fatigue and some cramping and frequent urination which I figured was a UTI and was right. The cramping went down around 7-8dpo but then around midnight today I had the WORST cramping that lasted maybe 10 minutes before easing off to minor cramps and then nothing after about an hour along with some back pain that didn’t really happen until then. I’m almost positive it wasn’t my cycle because I usually don’t start until 16dpo and that would be extremely early. I did have unprotected sex this month but he pulled out and it was either day one of my fertile window or the day before it officially started so I doubt it could be implantation. I’ve started back cramping extremely mildly today but it’s not even enough to take Tylenol and even more constipated than I usually am.