Been on Nexplanon for 2.5 years, last month I had 3 periods, and now a week later- sore and swollen breasts, and intense cramping could I be pregnant?

Hard to tell... It can be hard to tell if a woman is pregnant because some of the symptoms seen in early pregnancy can also happen in non-pregnant women. A urine pregnancy test gives a reliable result if done correctly. One can test about 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. An Ob-Gyn doctor can evaluate any persistent or worrisome symptoms.