Pregnant or sick?

 I'm 18, I went several months without having sex but in the heat of the moment me and this guy made the stupid decision of having sex without a condom, twice. I took the morning after pill the next day. This little event occurred about two days after my period ended.  About a week after taking the pill for about two days I was spotting.I usually get my period every 28-31 days. So I was expecting it  four days ago. After 3 days went by I took a pregnancy test in the morning and it came back negative.

I know sometimes stress and dieting can change your cycle. I have been holiday eating for the past two weeks and snacking on everything in site which isn't normal for me to do for so long (I'm back to my normal 3 meals a day/ no snacking). The past week my head mildly hurts and I feel slightly nauseated all day for several days now. I don't usually experience a lot of symptoms with my period besides my emotions running high but I don't even feel that. The past two months I haven't felt myself because a great guy dumped me and I just feel miserable with myself right now, no idea if that can be a factor. Past month I haven't been able to sleep well. I get maybe 4-5 hours of tossing and turning.  So, is it a change in diet?? Is there still a possibility I'm pregnant or is my cycle changing or maybe just late? 

I have no idea what's going on and doctors isn't really in my budget so that's why I'm asking you for help. Input please? Thanks ;]