Double check your pamphlet but you should be able to miss one active pill anywhere in your pack without it affecting your protection as you are on the combined pill. BUT there are a few combined pills that have different instructions. Try to stay on top of it and don’t let it turn into a habit. Missing the sugar pill is completely fine, they don’t contain any active ingredients.
The spotting and cramps are a normal and very common side effect for birth control users, they are most commonly experienced during the first 3-6 months but may still happen after that as well.