Does anyone know what could cause this???

When i was changing my 2 month old baby's nappy 3 weeks ago I noticed that the last few nappies had been a different colour (poo) so i looked closer and realised there was blood all through it. I took him to the GP and had a sample tested and it came back clear.. no problems supposedly.

Over the next two weeks there were still tiny flecks of blood in most poos and then there was another big one with lots of blood again. I took him back to the GP with the nappy and she said it looked like he had a virus as there was mucus through it too and he gets diarrhea now and then. She sent another sample which came back clear also.

It has now been 3 weeks since the first occurrence and I am getting concerned. The doctor seems uninterested, even annoyed by me taking him back so I will make an appointment to see another GP but in the meantime.. does anyone have any thoughts on what it may be??? He is a happy, healthy baby, gaining lots of weight, breastfed.. As far as I can tell there is nothing bothering him.. its just the blood, no other symptoms

I have no idea what it is but my doctor told me to be concerned if there was blood i my bubs poo or if it was black (after meconium obviously!).

I would definitely be getting a second opinion if I was you.