Question 6 year old laptop's cpu running below base clock of 1.9 ghz

Jul 27, 2021
So, my laptop that I've been using for 6 years has become slower in the past 2 months, when this started, i began noticing that my cpu was running at 1.5 ghz instead of 1.9, and also that there were random spikes in my cpu clock speed, at one moment it was running at around 1.5ghz and in the next 10 seconds it was at 2.8ghz and then it dropped back down to 1.5 ghz, I haven't even changed the power settings and I'm on windows 7 (because I tried win 10 2 years ago and it was really slow) this laptop has been working fine since i got it when i was 8, and i even played games on it like csgo, but now it runs like a TOASTER, I suspect that my new charger is to blame for this, since this started happening when i bought it, but my old charger broke. Don't tell me to buy a new laptop because I CAN'T. So how do I fix this?