BlueRose
Three boys---and one is a teen...wow oh wow... It sounds like your boys don't have any positive male role models in their lives. Am I correct? There are no males in your extended family who can fill the void? What about in their father's family? I don't want to alarm you but pervs often seek out boys in similar situations as your sons. Boys without dads or another strong male in their lives, long for such attention, thus making them vulnerable to the attentions of pervs. You have a lot on your plate but do look into perhaps placing your boys in programs that show them positive male role models.
Now as for you --- perhaps, as you suggested already, counseling could be helpful. Also, do some research. See if there are support groups for single mothers in your area. Oftentimes, the local Y will have such groups/programs. If there is a community newspaper in your area, check to see if they list support group meetings that fit the bill for you. If you can't find any groups locally, do some googling. You may well find an online support group.
Sad to say, so many of us these days don't have strong support systems in place. So...you are not alone. There is no shame in reaching out for help and support. So...please start looking---not only for yourself but for your boys, too.
Best of luck to you.