There are several reasons your therapist may have increased the length of your sessions. He may feel that half an hour isn't enough time to do what he thinks should be done. It may be, as you say, that he is thinking of starting you on medication.

If you can keep yourself from stewing over it, thats great. If you can't, call his office and ask straight out why he suddenly lengthened your session. You are within your rights to ask that and shouldn't feel intimidated to do so.

Sam2