Single digit MB/s throughout the day

I know this message board is more to just rant then actually get help, but I still have to post this to ask for help.

Running wired connection - 150 MB/s package - cat6 cable - all connections are secured - consistently resetting modem - DNS cache flush - and still my internet goes down to 2 or 3 MB/s at any time of day. Only devices connected to my internet are my computer and phone. I could understand internet slow downs during peak hour usage, but this has been going on for months, and frankly I feel like I'm just throwing money down the drain. If there's a magical solution out there to fix this, please tell me, otherwise ignore this post as another one of thousands of complaints