A while back, I subscribed to the myth that you need to glug a protein shake
no later than thirty minutes after your workout. Now I know better, I only have a protein shake if I haven't hit my protein requirements for the day for whatever reason, and when my current tub's finished I won't be wasting money on getting more. Besides the protein, I have never taken any other supplement. The clue is in the name 'supplement' - they're not actually necessary; none of them are.
If for some reason you can't get your protein requirements from real food, then I guess they're handy but for everyone else, they're a waste of money.
When you say pain, do you mean
pain! Or are you referring to a mild soreness? You should absolutely not experience any actual
pain while training - if you do, then you've overdone something and you should stop immediately. Soreness after training (especially a day after training) is normal and will probably go away once you get used to training.
If you haven't already done so, please dispense with the 'No Pain, No Gain' BS. It belongs in the 80s along with 'Fat Makes You Fat'.
Agreed; that's very good advice. The only thing I would say about stopping is it will cause you to lose at least some of your hard earned gains - it's inevitable. I would say at least do some resistance exercise, even if it's just bodyweight, and keep up your protein intake in order to maintain your current muscle mass. Some sort of weights would be preferable but bodyweight is better than nothing.