Ttc advice

Me and my boyfriend have 4 kids together already and we’re trying for a 5 we have been trying since 8/25/2020 with no luck I’ve been tracking my ovulation and I don’t think I’m doing it right I’ve taken at least 10 different test all negative I’m just starting to act take this seriously but I’m ready to give up any advice.! Atp I’m starting to think I can’t have anymore kids