My guy says he will dump me!

Dear Diana,My boyfriend and I have been in a relationship for almost a year. He used to be very nice and genuine. But now it seems as though he just does not care for me. I have tried to let him know how I feel but every time I do it, it just leads to us arguing. He now tells me that he likes another girl and says he will dump me. I really do love him and I really don't know what I would do without him. Sometimes for days, we don't see each other or communicate. It is clear that there is another woman in his life whom he prefers now. He has often pretended to like other girls and has pretended to dump me leaving me in tears. But now he is really doing it!