Gmail is a free, advertising-supported webmail, POP3, and IMAP service provided by Google. No doubt that Gmail are really tight in security from account hacking, spamming and unauthorized logins.
But, are you sure it is safe enough? Are you sure that you're the only person who logged into your account all these times? I am sure you will start thinking about it now.
If you're concerned about unauthorized access to your mail, you are able to use 'Last account activity' which is the feature in Gmail to find out if and when someone gained access. It's information you can use to troubleshoot unauthorized account activity.
Last account activity includes any times that your mail was accessed, using a regular web browser, through a POP client, from a mobile device, etc.