I did my first PT and angels didin't sing. OR My hair hated my first PT.

The angels didn't sing for me either the first protein treatment (PT), and my hair loves protein.  If nothing bad happened, that is a good sign.  If your hair did not like protein, it would feel hard and rough.  There is a small percentage of people who's hair feels very soft after a PT and/or gets straighter.

If you did not have a negative reaction:

1)You may need to do more PTs before you start to notice a positive change in your hair.  One PT might not have totally taken care of all your hair's protein needs.  You might be very low on protein.
2)  You may need to leave the PT on longer.  Again, you just may need more protein.  Leaving a PT on longer will get more protein into your hair.
3)You may need to try a different kind of protein. Soy and wheat protein work for my hair, but collagen is magic.  You may need to experiment with different proteins until you find the one that works for you.
Some proteins may work better for your hair then others. 

I had a negative reaction.  Does that mean I'm protein sensitive?

1)  You could be protein sensitive.  It could be that protein just isn't for you.
2)  Your hair might not have liked the protein in your PT, but will like other types of protein.
3)  You might need less protein or a different protein.  Ion Effective Care and Aubrey Organics GPB are milder PTs.  Keratin and silk proteins are easier for some hair to take.
4)  How long did you leave it on?  Maybe you need to PT for a shorter time.
5)  Did you do a deep treatment (DT)?  If you did not do a deep treatment immediately afterward, go do one now.  You need moisture to balance the protein.  If you only used a rinse out, you might need to do a DT to get more moisture into your hair.
6)  There is the rare wavy that likes daily protein in his/her products (gels, leave ins, etc.), but cannot PT.   Your hair may freak out after a PT, but love protein otherwise.