I think I'm pregnant and getting negative results

I'm a 29 year old mother of two. My husband and I usually use condoms but in the past couple weeks one night we just used the pull out method and one night we used a spermicide gel. In June I got 2 periods one at the beginning of the month and one at the end. My period is due around the 27th. Today is the 24th. For the last 2 weeks now my breasts have been very sore and nipples a little sensitive about 6 days ago I started spotting but only in the evening and thought I was getting my period early (again) but I would use a tampon over night and the next morning, nothing! This has been going on (evening only) for 6 days now an my breasts still hurt. I took a pregnancy test yesterday which would have been 5 days before my expecte period and it was negative. I've also had heartburn which I get often but seems more frequent in the last week. Can anyone help with any suggestions? Why would I get a period like I'm having which started almost 2 weeks early and only spotting anywhere from light to medium only in the evening an not even enough to need a pad or tampon for 6 days? And my breasts do Hirt sometimes before my period but usually not this long and seems a little worse. I'm going totale another test in 2 days because in three days I'm supposed to have a neck and back injection and can't if I'm pregnant (but would love o be pregnant )