When I was on injections, I sometimes got bruises but over 9 years, maybe 6 or 7 only. Are you using a new needle each time? I re-used them often but at least a couple of the bruises I got were from dull, overused needles.
Some other questions:
Are you thin or thick where you inject? (Thick is easier but I wouldn't gain weight just for this!

)
Are you pinching? (if yes, then try without. If no, try with.)
Is the insulin cold? The bottle or pen you are using need not be refrigerated.
Are you jabbing hard? (The needles are very sharp and need little effort. Try gently using them in an orange for practice if you need to.)
Let us know!