Had an abortion 4 weeks ago, had unprotected sex 2 weeks ago and now i have brown stringy discharge could i be pregnant ?

It is possible: Brown stringy discharge sounds like mucus with a little old blood in it, which doesn't mean anything about whether or not you are pregnant. (could be infection, irritation or just slight amount of menstrual blood + mucus) however, it is sometimes possible to get pregnant as soon as a few weeks after an abortion, a miscarriage or sometimes even childbirth. If you are concerned, get a pregnancy test.