Hackers, scammers, and others are constantly looking for your email and/or password hoping to use it for their own nefarious schemes.
While there are groups who will actively try to hack your account, there are others who are just as happy to buy or trade for your account details on various forums.
Luckily there are several groups of people who collect this data, but not for nefarious reasons, but to help others out. One such site, is https://haveibeenpwned.com/. There you can enter your email to see if it shows up as having been compromised.
Use a site like that to see if you need to change your password(s), or possibly your email address.