Sorry. Skype is used for many purposes besides social media so I misunderstood your comment above.
I suspect someone signed up for Skype using your email address. This could be someone who simply fat-fingered the address when they were trying to sign up, or it could be someone who did it as a malicious prank. With the precautions you have taken, I would not be concerned that your computer has been compromised.
What you can do is attempt to log into Skype with your email address you are getting these message at and select you forgot your password. Then hopefully they will send you a new password, or a link to reset yours. Then you can access the account and set the privacy settings.
Note this happens because companies are too lackadaisical when it comes to security and they do not use a two-step registration process where they send an email to the address used when a new account is created with a link to click on to "activate" the account. Instead, they just create it using the email address given. Then sadly, they sell the address to 3rd parties, or give it their affiliates so you start getting junk mail.
BTW, you can run MBAM with W10's own Windows Defender. That's what I do.
