My newborn vomits after I feed her both breasts. Am I feeding her too much?

My newborn is 5 days old and she feeds for about 5-10mins every 1-2 hours. She didn't have a problem feeding before and i was able to feed her on both breasts one after the other and always burped her after each feed with no problem. But since yesterday If I've fed her both breasts and burped her after each feed and she vomits after the second, and quiet a lot so now I've been only giving her one breast when she's hungry. I don't know why she vomits, she instantly latches onto my second breast after I fed her the first so I assumed she's still hungry but then she vomits as if I fed her too much. Am I feeding her too much in one go? is that why she is vomiting or is it something more serious? I'm worried that feeding her only one breast each time won't be adequate since she only feeds for 5 mins.