I think it's great that you kept trying with each baby and finally had success. Don't be so hard on yourself. The truth is all mothers learn as we go along and do things differently as a result. You tried to nurse each of your children, but the circumstances were different in each case. Don't let your guilt rob baby number 3 and you of a wonderful experience. Chances are your other kids will never even think about it, but if they do, just tell them the truth--that you wish you had nursed them longer, but circumstances got in the way, but that you love them all just the same.
Good for you! Its ok they wont notice the diference alot of moms i know who bf fed the 1st the longest and 3rd the least! It took a few trys to perfect it ok be proud of what your accomplishing now. I had mastitis and i probably woulda quit but i had a great lactaion consultant that was free and they told me to nurse through it baby help draw out the infection the first few week were harder than giving birth but now i have been breastfeeding for 24 1/2 months! Be proud of the gift you have gave all 3 babies!