Phentermine

Has anyone ever taken phentermine? I started it a few weeks ago and haven’t had any symptoms and it appears to be working. Recently I’ve had light cramping and I’m wondering if it’s from the medication. My bf and I did have unprotected sex on the 25th but we have been trying for a baby for a while with no luck so I’m pretty sure it wouldn’t be implantation bleeding. It’s just weird because i haven’t experienced cramping with it before and my coworker started it with me and has had no issues besides constipation lol. Just curious everyone’s experience with the medication