Need answers

Okay I’m 18 years old dating a 22 year old and we have a 11 month old daughter ... he as well has another daughter with another woman she has 2 other kids with another dude ...

Fast forward... about 2 months ago everything changed she came to visit “ Family Members “ and she stayed at his house and he would beg me to stay does nights but I was so tired I just wanted to get home and rest with my daughter so I gave him all my trust ( he didn’t live by himself he lived with his mother so it wasn’t just him and her in the house ) after they left few days passed and he was acting vary different towards me so I got a bad feeling I felt the need to check his phone but I didn’t wanna be that crazy but I really had a bad feeling so I did anyways ... he told her he missed her and they were flirting I confronted them and they both lied to me talking about we just friends... but the way they where talking ... I felt betrayed I feel confused I feel like I’m going crazy I feel like I should just ended ... he said he was sorry to give him another chance but I feel so hurt the fact that he lied the fact that I gave him all my trust and he didn’t give a fuck about my feelings... but I still stayed and decided to continue bc of our daughter but I feel like I did wrong but then I feel like I wouldn’t be able to move on I deeply love him but I still have a bad feeling he’ll do it again I’m scared to get hurt and I’m honestly feeling lost and I don’t know how to keep handling this ....