24 weeks and contractions while walking

I'm 24 weeks with baby #3 and was taking my normal evening walk when out of nowhere I had a contraction that stopped me in my tracks. It was painful and kind of scary. I had 4 more on my way back to my house (every 3 min) and then I got home, sat down and had 3 more (every 3 min) but now they're not painful and about every 4-5 min. Should I call my doc or should I be okay since they're coming less frequently and not hurting anymore?