I have never used numbing cream but I admit it took me some time before I could insert the sensor in a reasonably quick manner. I found out it is best to be standing up when inserting the sensor into the stomach which has helped. I use the Sen-Serter.
When you get the sensor, somebody will train you which will help so don't get overwhelmed all at once. It just takes time to figure everything out.
I have an acquaintance who had the same problem you did and the sensor has saved him! He wears his faithfully ever since going into a coma from low blood sugar and suffering side effects afterward. I am trying to wear the sensor consistently and notice a big improvement in my blood sugars.
The MM sensor needs to be calibrated six hours after it first starts "reading" your blood sugar. After that, it needs to be calibrated every twelve hours. Starting it out is the trickiest part. One thing that works really well is to insert the needle sensor before bed, put a piece of soft tape over it so it doesn't come out and connect the plastic paddle sensor in the morning. Don't even tell the pump you're starting a sensor until the morning when it has been in your body overnight. In the morning, you can cover the entire thing with a big Tegaderm so it's all enclosed. (The term "wet" means the sensor has been in your body long enough to give the green light on the plastic paddle and to start reading your blood sugars and sending them to your pump.)
The *most* important--and sometimes hardest--thing to do is to *only* calibrate when your blood sugar is stable! This means it is not going up or going down! That's why if you calibrate in the morning after waking up, it's usually a good time and before bed is good most of the time too. Otherwise, the readings are not very close to what your actual blood glucose is. If my blood sugar is going up or down I do not calibrate--I just wait 2-4 hours until my blood sugar is stable--even though the sensor alarms are a bother. That way I know there is accuracy!
You will understand more of this as you start wearing it and you can ask us later.
I have learned--over time--to appreciate what the sensor has done for me in showing when I'm dropping or going high.