Tbh I disagree with both comments above. If he did have an std test at the start of your relationship and he did have something it would test positive, whether symptoms were showing or not.
So yes, either he lied at the beginning of the relationship about having a test or unfortunately he hasn’t been faithful to you. However, there is a very slim chance that you could have had an std without knowing - because oral sex and other forms of sex can still transmit std’s (very rarely but on occasion), so it depends what you define as your first sexual relationship.
It sounds like a communication problem here. You do just need to talk to him and get to the bottom of it. Otherwise if there’s no communication and the trust has been broken, then that’s the end of the relationship really.