What are a few reasons as to why my lymph node can become immovable? i've had two pea sized occipital lymph nodes for 6 months and they have not changed at all and they are both immovable? and it said online that's its normal for me to feel them?

Pea sized nodes are normal. They are often found more often in sites where there is little or no surrounding fat or muscle tissue for them to hide in. With minimal surrounding tissue they may simply be attached there. Without an exam I could not be sure they were nodes or a cyst or even the knob like end of the mastoid bone.

You may feel the nodes every couple of weeks, if any of the lymph glands doubles in size, becomes painful, ulcerates, or other nodes become enlarged, or you develop fever, or lose weight, you should see a doctor. Wish you good health!