Just because it thins the mucous doesn't mean it helps you ovulate, and that is the problem. If you do ovulate, and still have thick, acidic CM then maybe it will help. If I were you, I'd chart your periods for a couple months and find out how irregular they are. They might be off by a couple of days, or a few weeks, or even a month or two. I know, because I also have very irregular periods. I am pregnant now, thanks to those ovulation tests (and of course my husband). You need to ask your doctor or midwife about this Robitussin thing. If the problem is that you are not ovulating, then I don't think Robitussin will help. If the problem is that your CM is too thick for sperm to get through, then that is a different story. I would definately not go solely on what people say on these boards. They are not experts, and I agree with you that taking a medicine all the time is not good for you. Good luck, and I hope your doctor, or even pharmicist can help you. It is very interesting.