Wages/overtime in pennsylvania?

I work in the state of Pennsylvania, at a rate of minimum wage. our pay periods at the 1st and the 15th eachother. the check pay dates are the 5th and the 20th eachother. its biweekly pay. i know the pay period days dont seem to work being some months have 31 days. the question is, i believe im labeled as part time. my hours work last pay period was 90.56 and i was paid NO overtime. i over heard the owners talking with some managers how they do not like givin over time. is it illegal that i was not given over time for working 90.56 hours in 2 weeks? and is it illegal that the pay dates are different days of they week, each week?