Hi Silvercat,
A little bleeding occasionally is not uncommon because as the needle passes into your body it can go through the smaller capillary veins. After all you prick your finger to get blood, so sticking a needle into your stomach isn't very different. If you are regularly getting bleeding it sounds like you are not injecting between the fat and muscle tissues, which usually means that they have given you the wrong length needle. If you can "pinch an inch" as the old Special K advert used to say, then you should be using an 8mm needle. If you have very little fat around your middle then you can get away with a 5mm needle. Also make sure the needles are 31 gauge (the finest), not the 29 gauge.