This self-doubt is going to murder me....One day I love my book and the other day I just want to delete it all and restart it...Any solutions to this?

Look at the first thing you wrote. I read it a few months ago and could see I had grown a lot with writing. If you don't like you're book you will definitly like it again if you see how much better it is than the first few sentences you ever wrote.

Honestly, just press through that feeling of hating it and try to find the fun. And when you aren't working on it, think about why you like the story, the characters, and the setting. A lot of the time the reason we feel negatively about our work, is because it is a source of tension. That tension colours our perception of it, and then we try to justify enduring the tension by judging the quality of the work, and if we find the quality is lacking we feel it was a waste, and on and on it goes. Try to remember nothing is forcing you to do this, it's something you get to do. I know it's hard, because there can be so much stress involved. But try to let go of the doubt, it isn't useful. Accept yourself and the work for what they are at the moment. They will both change in time, and it is better the change comes from a positive place than one of recrimination and doubt. Good luck!

Maybe... make finishing a condition of restarting? Like, tell yourself that once you've completed a bad draft, you're free to rewrite it from scratch if you want to. Then of course you don't have to actually delete the original, you just get to start on draft two.