It seems My girl Friend Is Playing With my Head And Emotions can any 1 help?

Im 19 kinda been used a few time so trustin someon isnt easy but i managed to find a girl hu treats me nice well thought she did till a couple of months ago wen i met her best mate now her best mate is nice enough and we became friends i saw more of her best mate i started to find out thing bout my gf i spose i should start at the start she told me she was pregnate i was happy but then she told me she drank to much and killed it by this time i startin to relise summats up then she tells me that baby still in her but not alive and doctor given her tablets every now and again she trys to make me jealous by sayin she sat in bed with other lads and she also ttells me she gonna kill her self then doesnt txt me next day sorry i worried to **** everytime this happens i get further away from her then 3 weeks ago she admited to cheatin me bein a mug that loves her forgave her dno y and ever since she been usin his name to piss me off like last week he supposedly dragged her off somewhere to talk but then she fall out with her best mate and her best mate says she was sat at home she is messin wid ur head i dno wer i am at atm can anyone help