You don't feel Braxton hicks in your vagina you feel it in your uterus. I had a lot of pressure on my cervix though during my pregnancy because my baby was so low, so maybe that's what you're experiencing
I keep getting those feelings too for about a week now the pressure isn't all the time but happens often. My discharge has also increased but I'm 18+2 so I'm going is normal!
Mine started to really get more frequent and strong at 32 weeks. It's almost all day long but yes it's your whole stomach tightening . Not your vagina.
I'm also 28 weeks, I'm in the same boat as you. Your stomach is gonna keep getting g tighter the bigger the baby gets, and the closer you get to your due date, the pressure will increase on your vagina. Laying down helps. When is your due date?