Having to reset modem several times a day

I've been having the same service at the same house for over a decade. The service has been wonderful. Hardly ever went down, minus a few storms.  

Out of nowhere, I've been having drops or slowdowns for the past week or so. I've never had to reset the modem this many times. After I reset the service is fine for a while(hours to a day) and then boom my 500 Mbps+ service is DL at 10 Mbps and UL at 2 Mbps. What fixes the issue is a modem reset. It's not any other part of the network. I made sure to check that all ethernet adapters are connecting at the correct speed(1 Gbps) when this happens. I never have to reset my router(PFSense).

I don't know what else to do.

I own the modem.