I had sex the 28th of November and my period was expected to be due the 3 of December (5 days later) but it never came and it's 13 days late now. I have a period tracker app on my phone and it is usually accurate tracking my period, a couple days give or take. I haven't had a late period this severe since I was 16 I'm 22 now. I'm not very stressed and daily living hasn't changed much. What concerns me is I continue to have cramps on and off like my period should be coming, but it doesn't. I've taken 2 pregnancy tests and both came out negative. Because I had sex so close to my period is it possible I could be pregnant? And if so is it still too early to show up on a test? How long should I wait before I take another test?

Yes it is possible. You need to be at least 14 days late to test