Can I 30F trust my 34M boyfriend of 8 months?

I am in a relationship that became serious during august of last year. Before the relationship was serious, we had dates for around 3 months (not as frequent dates as I hoped as he lived in a different city from me but has since moved). We kissed, had sexual contact, spoke every day and built a strong emotional bond in the 3 months before getting serious.

The first weekend we had sex and spent 3 days together was amazing and we were exclusive very soon after.
The relationship has had its ups and downs but something has affected my feelings towards him and I don’t know how to deal with it, details below.

I take photos with his phone and I was scrolling through them (he lets me do this) I stumbled upon lots of photos of him and another woman taken in august last year. The photos were what I would describe as couple photos and unnerved me.

My suspicious side took over and I decided to snoop through his older messages from august. I discovered messages between him and this woman from June-august and they were very intense messages. Where they would discuss their amazing connection and he would wish her goodnight and good morning every day. They spoke at length everyday and saw each other lots and definitely had a sexual relationship.

During the time we were building a connection I didn’t ask but I assumed he was not seeing any other women. I assumed this as he contacted me so frequently (everyday) and told me his daily plans. It now seems during some of these daily plans, when he said he was with “friends” or alone he was with this woman.

The only time he didn’t wish this woman goodnight in 2 months was the evening of the first weekend me and him had sex. However the next day he sent her a message to say how sorry he was and that he had left his phone at his friends and missed her so much.
After this message he continued the loving messages for around 2 weeks and during the time we became serious.

However he later messaged her to say they needed to talk and called her numerous times. He also sent some further messages to say she deserves better than him and she is amazing and he will miss her so much.
The communication stopped between them as he seemed to call it off and get serious with me and they have not spoke since.

However my image of him is now tainted, as I never suspected he was into anyone else except me. I also find it concerning how he can send this woman such intense loving messages while arranging to see me.

Do I have a right to feel betrayed and lied to? I know I shouldn’t have snooped, I have trust issues and my brain took over.

Any comments good or bad is appreciated. Thanks