Zoloft - Sixth week on Sertraline Still having anxiety Only on 37.5 and starting 50 mg How long do?

Hi, Mtnsgirl!
These medications do take time to become fully effective and you're on a good initial dose but most likely not enough to be effective yet. This is good though since it gives your system time to adjust slowly to the drug. Usually you'll see some improvements in the first few weeks but if not it's time for a dosage adjustment... which is what you're doing.
It can take as long as 6-8 weeks to feel the full effects and you can add a week or so after every dosage increase. Some people may even need to go up to the 200mg/day maximum because every person responds differently.
Another thing to keep in mind is that anxiety disorders generally take longer to respond to treatment.
Frustrating, I know! But try to be patient and stay positive and don't let your anxiety question if you're on the right track. It's important to stay in touch frequently with your doctor so they can evaluate your progress and make any adjustments to your treatment plan.
Something to consider if you're not already doing so and that's talk therapy like CBT (Cognitive Behavioural Therapy). The combination is much more effective than medication alone.
Hang in there... things will start getting better now.