Somtimes I go through 200 shells a day! It might be how the gun is fitting you! I have a semi and just got last year and O/U.
I had the same problem actually with all my shooting accept, worse! I used to get a scab on my cheek and continually rip it off the next time I shoot! Gross I know!!
Then i got some electric shaving powder and it worked great! I came to find out the stock was sliding and jolting up my cheek due to improper fit. Well long story short, I put this O/U up on my shoulder and I could just feel it!!!
it felt like an extention of my body! Problem solved! My hunting gun feels the same way and it's a pump! My 3" hunting loads feel like my handicap loads for trap!
I also feel that 3.5" shells are little over kill, I shoot 3" and do just fine some say the speed and power helps... NO OFFENCE TO ANYONE in my opinion 3.5" are for skybusters.