Pain and spotting on pill- STI?

Es

I’ve been taking the contraceptive pill back to back for over a year now (I have complicated periods so we decided to not have the period break).

Recently I’ve been getting occasional tummy ache which feels like period pain and I’ve been spotting.

I can’t be pregnant but could this be an STI or could it just be harmless spotting on the pill.

I’ve seen posts saying spotting during the first 6 months on the pill but I’ve actually been on the pill for 4 years...

I’m going to the doctors so will ask them but that’s not for a week so was just hoping you could help me in the meantime!

Thanks in advance :)