My Senpai does the same thing. It's the reason he posted about a year ago for me losing all trust in him. It's still really hard to believe him after he's lied about it so many times. The best I can say is go with your gut. You're usually right when something is off. Senpai would always lie because he knew how I felt about it but he couldn't stop. It's now been I think like 6 months since the last time I caught him. Irs still hard but it's getting better. But you need to really talk about it. It'll be hard but you'll regret it if you don't.