I would suggest 2 things:
- Hire someone to do an audit of inbound links for your website, or have someone in-house perform the audit. While it may be beneficial in some regards to move your site to a blank slate, your domain age (how long your site's existed) will be lost - that being a factor in SEO.
- Never hire anyone without knowing their tactics and requesting to look at prior projects they've worked on for your own edification. From what you've said, it sounds like the person you hired 2 years ago used some black-hat (risky cheat) tactics. It's great to have help, but unless you're informed about whomever's helping you, it will always have the potential to backfire.
