I would never recommend that u commit insurance fraud.
That being said, if u feel genuinely concerned about ur baby, then go to the ER now, especially if u feel no movement, have bad cramping, or lower right side (appendix area) pain, recurring sharp lower pelvic pain ( the key to that one is recurring = more ultrasounds) etc. If u have enough ER visits, they may deem ur pregnancy as high risk, & then u have many, many more ultrasounds.
If u want a better chance of finding out the baby is sex, then get really concerned & go to the ER in another week or two.
ETA: They WILL tell u the sex if they see it on an ultrasound scan if u ask. No one thinks that is weird, especially if you're worried u might be having problems. Women have pelvic pain all the time during pregnancy, & who is to say if there is a problem or not, unless they check u out. It is ur call, because ultimately it is a moral decision.
I had three super high risk pregnancies, & more than thirty scans with each. It was scary that they might find a problem at any time, but I also appreciated the reassurance that there were none.