Breastfed weight gain

I’m a FTM and my LO was 7 pounds 4.7 ounces at birth. At his two week appointment he hadn’t quite gotten back to his birth weight but my doctor was not concerned at all and since then my LO has gotten a lot better about breastfeeding. He eats every two hours for 45 to 50 mins until about 6 pm. He cluster feeds until 10 pm (at the latest) and then he will sleep for a good five to six hours and then we are back to every two hours. I can tell he’s growing but he is still so little. I don’t have a scale at home. He’s 8 weeks old today and we are still wearing newborn diapers and most of his 0-3 month clothes are too big for him. He has plenty of wet diapers each day and is pooping normally for a breastfed baby. I just can’t shake the anxiety that he isn’t gaining the proper amount of weight and I do NOT want to use formula. (Personal choice so please don’t be rude) His skin is wrinkled like he hasn’t grown into it yet. Any other moms experience something like this? His next appointment is in two weeks and I’m petrified to hear that he is too small.. help?