is there anyway to send an invoice to a customers email. After they purchase something from my form?

Yes, you can check out the new invoice feature on payment settings. When you enable that, you can set it up to be sent to the customer as an attachment in the autoresponder email.

Here is a useful guide for that: https://www.jotform.com/help/739-how-to-generate-an-invoice-for-your-payment-form?

Please try this and let us know if it helps.