Hi Kayye, hope you're doing better this morning.
I know that everyone is different and the fact t hat you can even get suction without lubrication is testament to that.
I would put my money on this being an issue rellated to moisturisation. If you think the trauma your skin is going through during the pumping process, I know it might feel okay but it needs assistance to stretch healthily. Baby oil is actaully quite an irritant so I am not surprised that it made you itch. Why don't you try a light vitamin E cram or some cocoa butter (added bonus of smelling LUSH).
None of us here are professing to be experts on teh subjects, or indeed have been doing it for long enough to really know the 'truth' BUT using a moisturiser is likely to not only assist with swelling into the domes, minimising damage to the skin and also possibly preventing strech marks. Please don't take this as patronizing, at the end of the day you know what is best for you but I would love it if you gave the lube a go.
much love,