Best answer by Mathis
Hmm, I'd recommend to go to your connection settings on a computer web browser to see if any Facebook account is still connected to your SoundCloud account. Also, on the bottom of that page, you can see connected apps - revoking access here will make sure none other then yourself can add any reposts or likes on your account.
Finally, to be 100% sure you're the only one accessing your account, you can change your password here. Afterwards, make sure you remember to log out of your account when using it on a friend's or public computer. :-)
Hope this helps