Do not put in a bigger fuse. You could cause a lot of damage. You most likely have a wire pinched or touching the frame somewhere. If it was working ok previously, think back of all the things that you have done and back track to look at those areas. I had a similar issue on a TT. I removed the taillights to reseal around them. I put the same screws back in the same holes and then it was blowing a taillight fuse. Well, in the end one of the screws had cut a wire. The way that the harness was just laying in the cavity it just happened to be in the way when I reassembled it.