Red blotched on neck and chest near shouler area?

i thing i had gotten these marks during my period before and now its happened again,and i think its happened the same amount of times ive been on my period and down there is very itchy sometimes,only during the time of the month,its been about 3 or 4 times where this has happened,its itchy yet also kind of painful,what could it be,do you think the red marks on my skin could be with my period too??? the blotches range in size from like masquito bite sizes on my elbows,to where there is around 4 or 5 on each arm and they arnt bited and then i have like bigger than quarter size marks on my other areas my shoulder and neck