Never, never, never put anything like glass into your butt. You never know but the glass could splinter or break and you would have some serious issues. If there is a stress fracture in the bottle and you hit it or moved it just right, it could break. It would be very uncomfortable in the emergency room getting glass picked out of your a##.
The blood is probably from the breaking of tiny blood vessels that line the anus. You need to be careful with introducing foreign objects up there. I am sure that you could buy a vibrator or a dildo and sneak it past your parents, unless they pat you down everytime you come in the door. You can buy them from any novelty store, like Spencers if you have one in your home town. They cost about 10.00 and are 100% safer than the toys that you use.