forgotten BC, yeast infection and bleeding, pregnant or STD?

Hello,
I am 19 years old and Im very bad at remembering to take my birth control pills. I have had to switch birth control twice because of constant spotting and yeast infections yet i have only been on the pill for a year. The birth control i am taking now only allows you to have one period every three months and I forget to take one pill at least every other week. I forgot to take the pill again yesterday so I took two today and found that i was experiencing another yeast infection with a slight pink color and bloody strings. I have been having mood swings and since i wont have my actual period until the end of april, i was wondering if there was a chance i was pregnant. i bought a pregnancy test but it says not to use it until 4 days before your period but Im afraid i cant wait 4 weeks. Im also afraid that having a yeast infection will affect the test if i do it early. Is the bleeding and yest infection from birth control or could I be pregnant? I recently had a pelvic exam and I tested negative but could i still have an STD? Im really scared and I need help asap!!!!! :-(