preseed

i know this may sound like a dumb question but here it goes. i’ve been off and on the depo for a few years and up until now i’ve stopped taking it so i don’t have periods to know if i’m late. me and my boyfriend have been actively trying for about 4 months with no luck. we used preseed a few nights ago and today i’ve just felt nauseous with a headache. and the thought of some foods could make me puke and insanely sore breasts. could i already be experiencing pregnancy symptoms (ofc if i am pregnant) this early if i was pregnant?