I second what Jackrose said, this was taught to me by the headmidwife from our hospital, she reckons she has yet to come across a blockage that doesn't clear this way:

Basically get your DP/DH to hold/support the opposite side of the breast while you use both hands to massage the lump...the counter-pressure from the other side of the breast is what gets the job done.

Also, since this has been a persistant problem, you should check out getting some ultrasound done, often that helps to unblock deeper blockages that you can't get to. It's also worthwhile if you've had repeated bouts in the same area of your breast, because sometimes the blockage isn't a blockage but a breast lump, which may need investigating.