Talk to Pediatrician on Teething Issue

Aoa! Kindly tag a paediatric. My baby boy is 3.5 months old and is exclusively formula fed (Meiji FMT-1). Over the last month he has developed this habit of sucking his fingers or hands all the time. For the last two three days he is doing it all the time, even while asleep. He is not drinking milk and he seems to have fever today as his body is warmer than usual. He has become very cranky and cries all the time. Also, he rubs his nose and eyes a lot and seems irritated. From last two days I have observed that his stool had green colour more than a bit. Can he teeth at this age?? What should i do to prevent this?? How should i increase his milk intake? We want to visit a doctor in person but cannot risk during this situation. He was born a healthy baby of 8 pounds but not gaining any weight now. Kindly guide us and advice on the above concerns.