Pregnancy Scare?

Ok so I got cramps the day before my period was due which is normal then the next day I was meant to get my period but nothing happened, more cramps but like not as strong as my usual cramps and now it’s been a week and my period still hasn’t arrived and I’m still cramping and getting headaches and feeling sick and I’m wondering if this could be anything else besides a potential pregnancy? I can’t take a test until my pay comes through next week either and I don’t want my fiancé to know yet because we’re saving up for a wedding in 16 months and I kinda don’t want a baby till after the wedding at least .... just so scared but I also know that stress can cause periods to be late but wouldn’t that also mean I shouldn’t be cramping as well? I’m 21 and have regular periods so this is so unusual for me and I’m actually so scared this whole past week ...