One hopes that you have Buildings Insurance? This is precisely one of the reasons such cover is necessary. They will (normally)pay to get it sorted apart from the first �500. The costs of underpinning, if required, typically run to several thousands.
If not, you are probably best seeking the advice of a structural engineer directly yourself - which unfortunately won't be free but won't cost too much (couple of hundred).
If the gaps are getting wider, you really need to do this.