Cycles suddenly got longer?

Ok, so my period has always been pretty regular, cycles usually lasted 25 days. My first time having sex was back in February and after that I had two 28 day cycles and my last was 30 days. Well now I'm awaiting my period and I am now at day 33. I have tracked my period for years and only went to 30 days that one time. I have had unprotected sex but not during what should have been my fertile window. Is it normal for your cycles to lengthen? Like is there a new hormone or something that gets released during sex that effects it? I don't take any medications and nothing has really changed since then  so I don't know what it could be. Any help is appreciated!