Might be preg on nuvaring?

Hi! So this is my fourth month using the nuvaring and I haven't had any symptoms at all besides feeling slightly nauseous the day after I put it in. My periods normally last 7 days or longer, and are somewhat heavy. I started my fourth nr Wednesday feb 11. I started my period on feb 13 and it ended on the 16, so only 4 days and it was much lighter than I normally have. Then for the next two days I had a tiny bit of brown/light red spotting. I feel nauseous on and off and so I took a hpt this afternoon which came back neg. I checked my temperature and it is saying 99*F. I don't know what's going on lol could I be pregnant but just not testing positive yet or is it prob just the ring? Thanks in advance for your help:)