20 weeks feeling a pop?

I was sitting down leaning forward to grab something and I felt kinda like a pop in my cervix so I sat straight and leaned forward again and felt it very lightly again but it stopped after that. So I went to the bathroom and nothing came out but I'm a little worried.. is this normal? I can't describe it any other way than a pop... I have an appointment on Thursday I'll make sure to mention it to my doctor but should I do anything before then? I feel light pressure down there but nothing too serious kinda felt like something was gonna come out of me whenever I stood up, that's why i went to the bathroom i even pushed a little and nothing happened. Is that just the baby kicking low?? The little one usually kicks a little below my belly button. Kinda felt like air coming out of my vagina if that makes any sense to any of you...