Completely normal reaction and feelings. I had 4th degree tear with my DS 2 years ago so know how you feel. I had shoulder dystocia, pph, pnd & ptsd and did a lot of counselling.
Firstly you shouldnt be in more pain, so make a gp appointment asap, you could have a small infection or stitches coming away and a course of antibiotics and someone who knows what they are looking at will make all the difference.
Next, keep up with your pain medication, paracetamol & ibuprofen by the clock rather than when you feel sore. An take things slowly, you may be just startig to feel a bit better and doing too much (that extra load of washing, walking a bit further than usual) will stress the muscles.
Try to do your pelvic floor exercises, even if you cant feel them properly, just keep trying. It increases blood flow to the area which will help healing.
Its still very early days, try not to beat yourself up about the ifs whys & maybes at this stage and just enjoy your newborn. It is very normal to relive it & wonder. Its how you process it, at the time theres a lot of hormones, emotions, thigs happen that you dont expect and you go into a survival sort of mode. Now the dust is settling you have time to start thinking things through. Speak to your gp or health visitor if you feel you want counselling.
Theres also a good support thread in the general health section called Raggedies. We have all had problems so may be worthwhile taking a look there for further support if things dont heal as you hope.