Hey L.,
First Congratulations on another pregnancy. And then onto your question. Everything in life is a mindset. Your gender disappointment is extremely valid. I can't sympathize with you because I have never set my mind on one sex. I know it must be hard for you, so I am not negating the fact that after 3 boys and still wanting a girl you would find disappointment in discovering you are having 2 more boys. The mindset issue is psychosocial and we all have a way to make ourselves happy or miserable. So what I am saying is that you at this point you have the choice to accept and become happy about 2 more baby blessings on the way. If you were someone who had struggled with infertility, the idea of 2 boys would be more than enough. Since you are someone with 3 sons, 2 more seems the norm and disappointing since you want a girl. I can only tell you that God has a plan, no matter how much we try to alter it. And that you must raise wonderful sons as he is entrusting you with 2 more when you were only seeking to add 1 more to the family. I am sure you are working to find peace with this and I know you will. Gender disappointment occurs only when we are set on having a specific gender. And the shock of twins is adding to the stress. I do hope you find resolution soon or seek counseling briefly to obtain a more positive perspective. Strength wise, you have done this(raised boys) before and know what you are doing.
Your expectations on what a daughter will bring are most likely not realistic. I say this not meanly but truthfully. Most often boys are closer to their mother. And while a daughter is usually more in touch with family once grown, there often is the teenage years were it can really go either way. The idea of dressing a girl up, dresses, bows and bracelets ends quickly. Wanting to plan her wedding, not likely to happen as she will be independent. And then,not sure which side of family your oldest inherited his bipolar d/o, but females are more likely to have it, therefore if any history of bipolar is on your family side, then you are looking at a 50/50 that a daughter would have it. As you already know, it is hard for the person as well as all family members. And conduct disorder is the diagnosis given in childhood when children are too young to diagnose as bipolar or antisocial personality.
Other things, but don't come too hopeful, is that the sonographer could have seen the same twin twice, or seen umbilical cord and called both babies boys. You should wait for more followup ultrasounds to know for sure, but in the mean time still prepare yourself for boys. It will be less reoccurring disappointment. As for other options, you could foster or adopt a girl. Some options are costly but some come with stipends and federal aid. Also look at your family size and income as a family of 7 or 8 will obviously cost more and depending on income could enable you to qualify for certain programs that would make it more affordable to add again. And then don't forget that the half of those girls that are not close to their moms, well when your sons date, meet and marry, they will need you. And you will eventually gain some daughters and hopefully granddaughters.
On a personal note, I am one of 4 girls, my parents gave up on wanting a boy. My husband is one of 3 boys. My parents have 4 granddaughters, we just can't seem to get a boy to save our lives, and my in laws expected only boys, but after one grandson, have 2 granddaughters. You just never know.
Boy or girl, healthy or sick, they are simply Angels from God, entrusted to us to care for as long as God has allowed us to borrow them. Pray for healthy or that you can handle what God is sending you. But don't get caught up in the specifics. My prayers for little ones are just simply that I can handle whatever God sends me and that the time I have with them is long. I tell other people that I never prayed for a healthy 10 toed baby, just a happy one. I pray that your next 2 boys are more than you expected and provide you the hindsight that they were meant to be yours.
May your disappointment dissipate and may you find the energy for 2 more at once.
God Bless and enjoy all your baby blessings,
-MB