Smoking first month pregnant...

I've always told myself as soon as I became pregnant I would quit. Well that's not so much the case. I'm only 3 weeks pregnant and I have a doctors apt tomorrow to confirm. Once she confirms I am pregnant I will not smoke. I just need some input, how badly am I hurting my fetus first few weeks of pregnancy. I've cut down drastically and am only smoking 3-5 a day max. Please no rude comments, I know what I'm doing is terrible & I feel guilty all the while.