I hope this doesn't sound new to you, hearing people complaining that their account were being hacked. So am gonna give you some few safety measures before that shit happens. Trust me its not only about setting strong password, more measures are needed.
Sometimes its your fault, yes your fault.
The following are the signs that your account might have been hacked.
1. Your account is following/unfollowing a lot of people without your permission
2. Uploading without your authority
If you can still access it, then you make whole process easier . All you have to do is
1. Change your Instagram password
2. Change your email password too
If your Instagram was hacked and you cant access it, then check out the new blog post