Two weeks ago I had a crown placed on a lower molar and now when biting or chewing certain foods I have a mild to severe pain in the tooth? Is this natural or something I should check into?

Not good. Call the dentist and go back.

One possibility is that some part of the crown is too high and s/he needs to grind it down a bit. I once had to go back repeatedly until the dentist got it right. Nearly had to have a root canal because the nerve got inflamed. Take ibuprofen to reduce the inflammation, try not to bite on it, ice if that's comfortable and get back to the dentist asap.

My dentist finally sent me to an endodontist who told the dentist how to change the shape of my crown so it wouldn't bother me. No root canal! I was very happy.

Did the tooth already have a root canal on it? Likely the crown is too high and needs to be adjusted... also could be that the tooth is cracked or has died (and needs to be extracted or root canaled, respectively). If it started 2 weeks after, it likely needs a root canal (if it was high, it would have hurt right away)

If the crown is high you have probably been beating the nerve up these past two weeks. Get it checked ASAP so you don't kill the nerve by irritating it.
If the tooth has already had a root canal you may have a cracked root and the tooth may need to be removed.