Your personal relationship is one thing, ownership of a business is another and you should have some sort of formal structure in place to cover off your business arrangements. Likewise, if you borrow money, the business should be borrowing it, not you as private individuals. Countless posts on here about people giving personal guarantees, mortgaging houses etc to keep a business going and it all ending up in tears
If you are subsidizing your boyfriend in terms of living expenses etc, that is a different matter.
Suggest you go and talk to you Local Enterprise Office as a starter, they can give good advice and support as well as courses on running business and financial aid