Medicines off limits while TTC?

I am feeling very congested lately and have a had few headaches but since my husband and I are TTC I have been very hesitant to take anything. Does anyone know what medicines are off limits while TTC? I'd really like to be able to use a nasal spray and something for my headaches but I dont want to hinder any chances of getting pregnant or an implantation that may have already taken place and that at the present time I am unaware of....