Nexplanon and phentermine boob issues

Okay guys. My nexplanon is coming out September 16. Which is 2 days early of my 3 year mark. Well June 6th I started on phentermine. (Iv lost 30 pounds) Anywaysss. So this past week my boobs have been really sore around the nipple and my nipple stays hard 24/7. There painful to the touch. Is this a phentermine issue? Or sence I only have a month left on my nexplanon? Or because Iv lost some weight maybe ? Any advice would help. Like my sports bras litterally have indentions in them now where my nipples are hard 24/7.

Also no, I am not pregnant. I took a test at the doctors office this past Friday when I got my phentermine refilled.