Irregular period

Me and my partner have been on and off TTC, we had intercourse (unsure whether I would have been ovulating) anyway, I did a pregnancy test before my period was due as I've had a lot of tummy pains, not so hungry, tired and feeling bloated (test came back negative) I came on my period on Friday and by Saturday night my tampon was clear. I usually have 5 day periods. So I'm a little confused?! Anyone had this or have advice.