What do you guys think this is

So I had sex with my partner and I am used to getting cramps afterwards but this time it was different the day afterwards I had cramps so bad I felt them in my stomach and my back at the same time it just freaked me out this that normal I have never had them so bad like that just from sex but I am on day 17 of my cycle as well(learn more on Glow: https://glowing.com)