Rome: Total War having problem with other Roman Families.?

Okay so the imperial long campaign was going smoothly but until now. All of the families and the senate cancled there alliances and there military acceses with me, and my only ally left is numidia (who I will be destroying shortly), and now I see Brutii armies going through my provinces, heading towards them, all over the place! They are very strong and I do not have the man power to get them off. In diplomacy, alliance is not a choice. So what do I do? I still need to conquer the British Isles (have an army up there doing so) And a very fortified Brittanic region near the Brutii border (have 2 or 3 armies on there way there), And I still need to send armies to invade Numidia and Carthage! What should I do!? Please answer and thank you. By the way I am playing as Juilii if you have not already guessed. Okay again thank you.