So sorry to hear about this Marianna! Just for the record, you and your fiance look fabulous - it's just that the photos aren't quite up to par.
You were saying you need to find out if there's anyone else available, within budget, and at very short notice, before you cancel - and you know what? I think I would cancel anyway - even if that meant I didn't have a professional photographer on hand. I don't know how much of a deposit you put down, but to me - it isn't worth the trouble to try and explain to the photographer what you didn't like about the engagement photos and then *hope* the photos are better for the actual wedding. Not if you'd end up paying the full price. In fact, I think I'd feel funny (worried, awkward, uncomfortable, nervous) posing for photos for someone who I'd already 'had words' with (re: quality of photos) etc.
I recommend canceling - and trying to find someone else, while *also* putting out a plea to friends/family members to take tons and tons of photos, and asking around if any of said friends/family members know of people who are 'into' photography and would love a chance to take a bunch of pictures on your wedding day.
Once again, I'm so sorry about this stressful scenario...aggghhhh....
The sooner you get it dealt with and resolved, the easier things will be though.
Hang in there, and you *do* look beautiful.