Practice makes perfect, you know the saying no gain without pain.
Seriously, if you suffered that amount of discomfort, it can be either the equipment you were using not being suitable. Our as a first timer you spent the night worrying about all the spooky things and noises going on around you.
Sadly at this time of year, as the night draw in the levels of damp in the air do cause one to feel cold.
At this early stage of your outdoor life,I would not worry about your tent being unsuitable, as willem pointed out cold rises, and as we have had a few rainy days of late the ground will be very damp, so making your groundsheet feel more the colder thus you need to tackle the problem from the ground up.
Regrettably comfort cost money, ok you can go to poundland and buy a sleeping mats there for a pound, but they are as good as useless, you will need to either shell out and buy the type of mat recommended by willem, or buy a 3 season polyfoam sleep mat which will be cheaper but not that cheap but more bulker.
Now to sleeping bags, for camping at this time of year, you really are starting to need to look at a 3 season bag as I have already said, night time temperatures are starting to drop. So you have the choice of down fill(expensive and compact) or Synthetic fill (Cheaper but Bulker). One reason peeps get cold is they buy a sleeping bag which is the wrong size for them, when buying sleeping bags, you need to get one which will allow your body bulk to move around comfortable, if it is too tight then you will lose body heat, where the material is pulled against your body likewise it need to be long enough so the shoulder baffle fits snugly around your neck