I heard somewhere that smoking reduces your sperm count. Is this true? How else, other than being a carcinogen, is smoking harmful?

I'm a college student who is struggling with the decision on when to see a doctor for treatment with my depression symptoms. I believe that I need to get treated for depression, but I'm just as scared about not getting treatment as I am about starting antidepressant drugs in my current lifestyle. As far as I can tell, I'm exhibiting the classic symptoms of depression, and have been for a while — frequent crying fits, days where I lose all motivation, and sometimes, even thoughts of suicide. But I drink frequently, almost every weekend, and use marijuana occasionally, and I am quite unsettled by the possible interactions between antidepressants and these other substances. In my day to day life I do very well — I hold a good GPA, have good relationships and a good social life, function well most of the time, and stay in shape for sports. I don't intend to change my lifestyle significantly to make room for depression treatment. But when do I need to get help? I don't want to force an unnecessary change on myself, but I don't want to put myself in danger from depression, or even worse, from the drug interactions between antidepressants and alcohol or weed. What is the tipping point?