Totally normal, and eventually they will stop catching the bugs and viruses because they've already come across them. For some children, it can be a problem though, and how you manage it is up to you, and your DH needs to be supportive of it.
DS2 suffered constant ear and throat infections, and at 18 months he was eventually referred to an ENT and had to get his tonsils removed adenoid trimmed, and grommets put in - but that was a 6 month wait. (Because he was under 3, only the head ENT could operate on him, so we couldn't take any last minute cancellations either). After that, he was brilliant, and stopped getting ill.
The problem is you don't KNOW which way it's going to go, whether he will stop getting ill, or whether there is something more at play. But not knowing is ok. If you're managing now - as difficult as it is - I would suggest you keep going. However, plan for the alternative so that should you get to crisis point - your DS is ill too frequently or your work won't let you take more time off - then you can follow through with your emergency/crisis plan.
I don't think you should quit work just yet though.
Oh and Childminders can be brilliant! Your DC get more individual attention, get to go on 'outings', they will often go to play groups, and they are in a home environment. My 2 went to both nursery and childminders, both were brilliant in their own way. But, if the childminder is childminding because they have young children, if THEIR children get ill, you will also have to take time off work to look after your own children. Happened a couple of times to me.