I am going to try to put this in a diplomatic manner.....apologies if my words are harsh though, as I cannot rightly think of how to voice my opinion without it sounding tough.
OP - first off, I know some of what you feel. It took three years to conceive our ds2. It is different for me, as we had already been lucky enough to have our first son....so I did not feel as you do, having not had a wee one at all yet. Still though...a 2nd child was very much longed for and continually proved elusive, so I do appreciate a little of what you feel and say.
However, I would not have dreamed of putting a blight on anyone else's happiness in getting in the family way....which people we were close to did, within that three year period. To place yourself on centre stage in someone else's show, like some sort of tragic heroine, is beyond the pale. To then expect them to symapthise with you and take your issues on board themselves, to the point of having to walk on eggshells around you to protect your delicate feelings is very self centred.
You say you have been TTC for seven months (which as others point out, isn't that long) and by your own admission have spent those 7 months keeping your feelings to yourself and crying alone. Did you think you would snap your fingers and a baby would come along? Whatever is wrong with being patient, like everyone else has to be?? NONE of us can demand a baby to order, yet you feel slighted because it hasn't happened immediately? You have then passed those self centred and unrealistic expectations on to your brother, in an attempt to make him and his wife feel guilty, because they have been lucky enough to fall pregnant quicker than you will! Where do you get off doing that?!
Your 'apology' email pinpoints that you feel entirely justified in your actions regarding this....as you are still determined that it should be about you and your situation, rather than rightly about them and theirs. They have not stolen your thunder....they have not done it to hurt you....they are not responsible for your situation!!
Be mature and exercise some adult patience OP, and use some manners from here on in. Recognise that this is not all about you and behave accordingly. Your conduct has thus far been pretty dreadful.
7 months is no time at all when TTC - understand that, and be happy for your brother and his wife, who have been fortunate enough to conceive sooner. It's not a competion, and you have no exclusive rights to be the winner. You CERTAINLY have no place forcing others to swallow your sour grapes.
Remember...an apolgy isn't an apology if it contains a 'but'.
Very good luck in TTC...I hope it happens for you soon xx