I have a four month old baby and I was taking lowest form of birth control because I was breastfeed. Well I got sick and I was taken the birth control while taking my antiboctics and stopped breastfeeding and I had unprocted sex. Now I have completely stop breastfeeding and I haven't started my perdio yet could I be pregnant... I am now starting to get uterus cramping and stomack cramping and feel sick..

Yes, you could be pregnant. Even used perfectly, birth control is not 100% effective and some antibiotics, such as rifampin, greatly reduce it's effectiveness.

How long should I wait before taking a test

You want to wait for at least a week after the expected start date of your period and test with first morning urine. If you still aren't sure, see your doctor and ask for a blood test.

Yea I took a home test but it came out negative so I think its to early. So I have been breast feeding for 4 months and I am not making enough milk for him so I use formula also so could that have increased the chance of me being pregnant... I stop taking my birth control a day after I had unproctect sex because I kept bleeding off and on every week for two months and I always forgot to take it on time or I would miss a day would that have lowered the effect to?