Idk how to feel😟

My SO woke up early this morning before his alarm to ig take a shower or something. I hear something in the bathroom and it is him jerking off. I looked at his Youtube history because he was logged on in my phone and he was looking at girls shakin their asses and jerking off and when he came out the bathroom i told him i heard him and he kept trying to justify it and idk he deleted his Youtube history now and he called me trying to make sure i am ok. But idk how to feel. Been dealing with him 8 years on and off and i thought this was it. we are finally getting married and now this ughhh!!!!!!😡😒😒😟