Yes, Seiza, it is and will be painful for sometime to come but do not worry as the more you practise the easier it will get. I have had the unfortunate experience of breaking both the bones of the lower leg and of shattering my heel, both times this made sitting in seiza almost impossible to bear. The solution I was told and tried with great success was to put a pillow under your backside when you go to sit in seiza, this takes some of the pressure off an enables you to gradually sit in seiza for longer periods of time and of course eventually to sit comfortably without the pillow in the dojo. I recommend that you only practise this method at home as taking a pillow into some dojo may be frowned upon. Hope this helps.