I've always heard that it's recommended to get it at 28 weeks. It will protect you from being sensitized for 12 weeks and more or less suppresses your ability to make antibodies if somehow the blood ever did cross. There are risks to it, but you would have to weight the factors on each other and see what's the best choice for you. Some don't want it because it's a blood product from other people, but everyone is different and for some this isn't a factor to them.
I'm sorry I've never had any issues with that so I don't know what to say. Hopefully someone else has some experience and can help you out.