Not sure how helpful this will be but this is my experience.
I have finally made it to chapter seven of the story I started years ago. Many times I went back and rewrote from the start, changing point of view, changing tense and changing the starting point. I could not move forward until I was happy with it. Now I am confident enough to trust the foundation I have built and keep building on it. So to get past the constant rewrite, I had to do the rewrites and explore. If nothing else it was good writing practice. Plus, throughout that time I wrote other stories as well such as fanfiction and short stories and got feedback; as well as reading other people's work and giving feedback. People told me to not go back over it and to just keep writing but I could not but persevering paid off and I know I don't need to rewrite anymore.
Another problem that can come up is, for whatever reason, you come to a point in the story that just doesn't speak to you. It isn't necessarily boring, it might be about something you don't have much knowledge of or a emotionally difficult scene. In this situation, what worked for me was working on something completely different to help get the creative juices flowing and while you are on a role, jumping straight in to the difficult scene and keep writing. When you feel your momentum falter, push on and you will reach that point where it gets easier again and you can go back over it to clean it up yourself and/or get a beta or friend to look over it.
The other writer's block problem I have experienced is having too many ideas bouncing around my head and not being able to concentrate on one thing. What worked for me is to either write down the premise if it was story ideas or write out the scenes to points I could come back to later. I have word docs with pages of scenes and synopsis for stories I have yet to get back to but getting them out of my head meant I knew I wouldn't forget them so I could forget them until the time comes to use them and I could focus on what I had committed to.