did i miss my shot this month?

today is cd 20. it's the third day of a positive opk and it is the strongest positive today. we weren't able to have sex yesterday which I think was my most fertile day 😣. we did it on cd 16,17 and 18 and plan to tonight on cd 20. Do you think I have a chance this month? I'm worried because I tend to lack ewcm so I don't think sperm can survive very long in me. thanks for the input!