We typically advice applicants or beneficiaries of the H-1B Visa not to change employers without the new employer filing the petition first. The case doesn't need to be approved but they should at least file the I-129 first. Receiving those receipts is super important to show that you have done everything properly in your transferring of employment. The new job should be one from a similar job industry as the one you have it. If you're in the U.S., you can remain here as long as you maintain your status some way. Simply filing in April is not going to protect you until your I-129 is actually pending, so you have to maintain status somehow for at least several months. A lot of times we don't hear back from USCIS with information about whether or not your case was selected or when it's time to file until May or June. This may leave a lot of individuals in a kind of limbo.