If (say) I borrowed money from a loan shark and haven't been paying him...?

the agreed sum per month because of financial difficulties, the agreement was writen without the consultation of attorneys. Now because of financial difficulty agreed monthly payments cannot be properly adhered to which has produced the loan shark to calling with threats of using his lawyer(who is his son) to seek legal action.The total sum of money was borrowed with a cosigner. From what I have researched loan sharking is illegal to begin with because they arent licensed to lend money and do not conduct collection by gov guidelines but is it illegal in texas? Can i be sued in a situation like this? and what will be the consequences?