Is it normal to have extreme pain at start of teeth whitening treatment?

Some people just have very sensitive teeth when it comes to whitening, especially if they have gum recession.  There are some fluoride gels that can be used immediately following the procedure,  but sensitivity sometimes still occurs.  If so, you may not be a good candidate to whiten.  

From the sounds of things, you may need a lower concentration of gel in a take-home whitening kit.  For patients of mine that are this sensitive to teeth whitening, I recommend using sensitive tooth paste for 2 weeks prior to whitening, then going straight to take-home whitening.  I would not recommend attempting in-office whitening.  Good luck and I hope this helps. Sarah Thompson, DMDReal Self 100

If your teeth are sensitive after 10 minutes of whitening strips then they will definitely be more sensitive during/after the in office power whitening with a stronger gel.  There are gels you can use at home to help reduce sensitivity but I would suggest that you try the at home custom whitening trays with a lower strength whitening gel (10 or 15%) which will have a reduced risk of sensitivity.