My baby is 4 months and she is not getting enough of my breast milk (I think). What could be the solution because she feeds on my breast like the whole night.

Sometimes, babies can use the breast as a pacifier (soothing agent) and will thus seem to feed for long periods. The best way to know if your baby is getting enough is by:
<ul>
<li>She has regular wet diaper 6-8 diapers a day and bowel movements.</li>
<li>She has consistent weight gain at every clinic check.</li>
<li>You can here audible swallowing sounds as your baby feeds.</li>
</ul>