Sick again!

So it seems like Lincoln gets sick every other week. Are we doing something wrong? He seems to get every bug out there. He had a little bit of a cold on Wednesday, but I took him to the Water Mine to go swimming anyway. That night I checked on him while he was sleeping and he was breathing really fast. His chest was rising and falling really fast and as I lay down next to him, he was moving me with his body. I should have taken him to the ER that night. I feel like such a terrible parent. I didn't realize it was that bad because his face didn't look like he was having a hard time breathing. Anyway, I took him in the next day and he didn't look very good. Our friend and doctor said he had Broncheolitis and maybe phnemonia. His chest sounded terrible. And he was pretty close to needing to go to the ER to get more oxygen, but not quite that bad. Anyway, we did a few rounds of the nebulizer while we were there and he sounded a little better, so we took it home and today was the last time we needed to use it. I was so surprised at how well Lincoln did it. I was worried he would fight it. But he got to watch Pooh Bear and eat M&M's so he was happy. He's much better, but still has a runny nose and a cough. it seems like he is always sick. Is this normal?