Hi, I an 24 years old. I'm 5ft and weight approx 7stone 6pounds. I have recently changed contraceptive pill to cerazette . I bled after one week of being on this pill. It has now been just under four weeks and I have started to get back ache, head ache, heart burn and mist unusually, a stitch-like pain in my left side. I took a pregnancy test three days ago but was negative. however beleive there's a small possibilty I could be pregnant due tofact my fiance and I didn't use condoms during the change over in pills