Tommysmum - it is always scary seeing blood when you are pregnant. However, it is very very common. I had it also with a couple of my pregnancies (one of those is a gorgeous 6 year old boy!) As you would know brown blood is old blood - again not uncommon around this time of pregnancy.
You could go in and get an u/s now and at this stage you should see a beautiful little heartbeat. That may be a way to put your fears to rest and also to have a peek at where that bleeding is coming from...