Hah, welcome to my world. DS is 12 weeks old and has already outgrown his size 3-6m bodysuits. In fact, he is curently latched on whilst I'm typing this (thank god for the iPhone!) and I'm desperate for the loo!
No wonder you're tired - I would like to say it gets better, hang in there hon... but my DS was the same and BF every 3 hrs (day & night) until he was 8 months - and I started weaning him at 4 months!!
Just make sure you get support so you can have a break. Even if you have to struggle to pump some milk for someone else to do the feeding on one of the feeds while you have a rest.