please help!!

Lindsey
So I need some advice. I'm currently pregnant with baby #4. After having 3 boys, this is a much anticipated baby girl!! I previously tried to breastfeed with all 3 of my boys but was unsuccessful. Besides major engorgement every time, I ended up with severe mastitis 2 times with my 1st 2 and with my 3rd as soon as I got it with him I couldn't handle it so I quit.  My sons are ages 12, 9 and 5. I know information has probably changed or evolved just even in the last 5 years. My dilemma is I remember being told with my 1st pregnancies not to express milk to relieve pressure because your body will try to keep up with the supply and demand and could cause more problems. But I've recently heard that after the baby nurses to go ahead and express what's left in that breast to help avoid clogged ducts and to avoid mastitis...... so this is my confusion. I of course will plan on trying to breast feed this child but I'd like to be more successful then the past has been. I will also be talking to the lactation consultant at my next doctor appointment but I'd love to know what's worked for you and what advice you have been given. 
I'm also aware that your told to nurse through the mastitis, use heat and cold to help with swelling and everything but with my last time getting it I had to take 3 rounds of antibiotics to get rid of it and by the 3rd round of antibiotics my milk supply had really dried up and even pumping didn't help then. 
So please please please tell me your stories and what's worked best for you! 
Thanks!!