Will my ss be affected if I drag my pump time from 3 to 4 hourly? TIA!

The short answer is - it depends. It depends on how much time you have to drag your pump. Say for example, your body is currently trained to pump 200ml every 3 hours. You need to teach your body to pump at least 200ml every 4hrs. What you need to do is when you've ensured that your supply has stabilised at the 3hrly mark, drag your pump by 3.5 hrs, do this consistently for 3-5 days, and if you notice supply dips, cut back to 3 hrs, wait for it to stabilise and then start again. When you've managed to stretch it till 3.5 hrs, repeat the process by stretching it to 4hrs. Some can do it faster without following this method, but some will see a drop in supply. You know your body best, your call.