how do i see if it's the guy i'm dating really losing interest or it's just my anxiety/attachment issues?

i tend to overthink and get anxious a lot but at the same time i can often see someone's intentions quite clearly. how can i guarantee if my feelings are a result of my overthinking and low self esteem or are they real? i have no one to ask for opinion irl and don't want to ask him directly as we are dating for only a bit more than a month now