My baby is not drinking enough milk. pls help?

my baby is sleeping as soon as offer her my breast. it wont take more than 10 minutes usually. i tried to make her sleepy by rocking her, and it sometimes take an hour or half an hour for her to fall asleep. but when i offer her my breast she would doze off within 10 minutes. i tried to wake her but she wont wake up. and im worried if she is taking enough milk. but if she is not sleeping she gets hungry really soon, sometimes within half an hour. so should i wake her within every half an hour while she is sleeping? and is it a problem that she is sleeping like that? she is now 2 months old and urinates more than 6 times and is gaining weight. but still im worried. please help