Mason health update!

Three weeks ago Mason weighed 10 pound 5 ounces (his birth weight) His doctor was concerned because he hasn't gained weight (he was 9lb 9 oz when he came home from NICU at one week old).  We had to give him rice cereal in his bottles and go back in a week. When we went back he had actually lost 3 ounces!  His doctor sent us over to the hospital for some blood work and an x-ray of his stomach. We got that all done and stayed at hospital to find out the results. Everything came back normal! This was on a Tuesday so the doctor said she wanted to see him on Thursday and to give him some formula. When we went back Thursday he had gained his 3 ounces back! The doctor was happy with that because she said babies should gain an ounce a day and he gained 1.5 ounces a day.  She said she wanted us to come back in a week which would bring us to last Thursday the 21st.  Mason weighed 10 lb 8 ounces. He gained another 3 ounces, but he should of gained at least 7 ounces =(  He now has to see a stomach doctor and have an upper GI done.  She also noticed he has a small heart murmur. When he was born his PDA in his heart didn't close like it should have, but the NICU Dr. said it wasn't anything to really worry about.  His primary Dr. said she would rather check it out then to just ignore it so he also has to see a cardiologist on July 12th.  We're obviously hoping that everything is normal and he's just a tiny baby. Which would be weird seeing as he weighed so much when he was born, but I would rather have a healthy tiny baby over the alternative. He eats every 3 hours and doesn't spit up so it's not reflux or anything like that. We just need to find out what's going on and quick- I am SO annoyed of hearing people say how tiny he his or oh he's so skinny! He has to go back to dr. on Thursday the 28th so I'll update again after that!