So basically, I had Gmail as my backup email, so when I got some emails on my Proton account, it sent messages to my Google email saying that my Proton email had received messages and who they were from. They were regarding purchases I made, so it basically defeated the purpose of leaving Gmail if Proton sent them my purchase history anyways.

I removed the backup email and it fixed the issue. It still pisses me off. Also Proton tried as hard as they could to force me to collect all my gmail spam in that account. I got around that by making a bogus gmail and then signing up to proton with that, IIRC.