how can i obtain text messages in pa,wife admitted cheating but i think something is still wrong

As far as I know, you can't.  It seems that the phone companies do not keep a record of what is transmitted by text, but check with your carrier.  If they do keep them, and the phone contract is in your name, you could request the records.  If not, you would need to subpoena their records.  If you have this kind of trust issue with your wife, I would recommend counseling to work through it.  If you are thinking divorce, you should consult with an attorney in your area, who will likely tell you that whether she's been cheating or not, there is not much impact on a divorce, except possibly in the support arena.  Good luck.