Hi, I Was On The Depo Contraceptive Injection For Over

Hi, I was on the depo contraceptive injection for over 3 years and started Noriday on 23rd Dec which was a few days after my next injection was due as I didnt feel happy with the weight I had gained on the depo.
I missed a pill last Thursday but took it as soon as I remembered but me and my partner had unprotected sex.
I have started to get pains today similar to period pains but with having been on the depo for so long I can't actually remember when my period would be due. I'm just a bit scared now as I'm still young and wouldn't be able to afford a child if I were to be pregnant but I'm sure it would be too early to tell at this moment in time if I were or not with it being less than a week since the unprotected. Just wondering if it may be a side effect of the noriday as I had this issue with cerazette when I was on that about 6 years ago