paw/leg limping,worse when been lying down …nothing to see

my 8 yr old cocker has been limping on his front right leg for a few months now ,i keep taking him to the vet ,but he wants to opperate on hid back one .which is not the problem at this time if i look at his paw he gives me a soft growl just to say i,m sore ,, i have looked between the pads ,,looked at his nails(the vet said there ok) but it seems like the little bones just back from his nail ……i hate myself for not making him better , ,,, i walk him on grassy land cut short and on the beach ,, i encouraged him to paddle to try and see if the salt water would heal whatever is wrong ,,,,,,when he has been lying down he limps more for a few minutes when he gets up …he does,nt cry with it ,,,but as i said allows me to know to be careful if touching it .can any body help i feel so sad as i always make him better ,,,,,thanks …………………………….barbara ,,,,,,,,,,st ives cornwall