First of all, this is a problem that happens to many Instagram users, so please do not worry! While it may take anywhere between 3 days to 2 weeks to recover your account, most users will have it recovered.
Meanwhile, here are some things you can do to speed up the process:
1. Fill in the form here and select the option “I can’t add my email to my Instagram account because it is already in use.”
2. Email Instagram at firstname.lastname@example.org and explain the issue.
3. Send Instagram a message on their Facebook page here.
4. Log into another Instagram account and click on “Settings” > “Report a Problem” > “Something isn’t working”. Type out your problem and remember to reference your account username.
5. Tweet @instagram with the hashtag #instagram with your problem.
6. Try logging into your account from a different device and click on “Learn more”. You will be prompted with a form to recover your account like this image.