Positive opk 7dpo

Michelle • 34, DH 37. ttc #1 for 4+ years
How's this even possible?!? Today I just decided to take an opk randomly bc I'm getting an MRI on Monday and don't have any pregnancy tests.. Wanted to make sure I'm not pregnant before going. I know that opks should never be used as hpt's but this test was pretty positive. Should I go out and buy an HPT?