My cousin is currently pregnant with her 3rd. And around 4 months she started having what seemed like a full period. Dr said her cervix was tore and it's from lifting heavy objects (probably her chunky babies Lol) but now she's almost six months and the bleeding has stopped they told her it's "nothing" to worry about and just keep from lifting.
My wife don't have a tear but they recommend her to do a cervical cerclage because of a past MC. Hope you can talk to your doctors and see if that's a option you have. All the best to you.