For your employer not to pay you once is shocking. For you to allow it to happen twice is stupidity. Why you haven't kicked his door down or "blocked in" his car/helicopter is beyond belief !
Don't ASK what is going on .. . . . DEMAND to know when you are being paid and if they are being unhelpful then go to a Citizens Advice Bureau pronto.
In the meantime carry out no further work and get looking for another job . . . . . .fast.
Tarman