Is this adultery?

YOU CAN CERTAINLY DIVORCE YOUR HUSBAND based on adultry but unless he admits it, you would have to prove it.  actual catching someone in the act is not necessary.  if you can prove the "opportunity and inclination" that usually is sufficient.  It is not necessary to go through the time, expense , either out of pocket, mentally and physically to get a divorce.  There are other grounds, such as cruelty, either mental or physical) desertion, irreconcilable differences, no fault, 18 months separation just to name a few.  They will all end up with a judgment for divorce.  Usually, adultry has little if any effect on the money issues.  The rights of the parties are usually the same and the courts do not use distribution of property or spousal support as a "punishment" to either party.  Your rights are your rights, his obligations are his obligations.  Good Luck