Help...

Hello everyone. I’m new here and could use some advice😣

So I’ve been dating the same guy for 3 1/2 years now and I’m having some major emotional issues with him messaging another girl. Back story in short: him and this girl have been friends for a LONG time. But every time she’s down in the dumps she always messages him and dogs herself and he always tells her how special she is and how pretty she is etc. I know she isn’t surrounded by good vibes and stuff, but something in me just gets so upset anytime I see her name pop up on his phone..

From me I don’t know if I’m being overly jealous or if I have probable reason to be upset... help.