Why couldn’t you get seats together? How far away is ‘soon’?
The reason I ask is that could affect seat changes.
You couldn’t get seats together - does that mean you do already have seats booked? Which seats? And which airline? Some are more accommodating than others.
If you have time before your flight (in other words, you aren’t flying tomorrow) call the airline. Be prepared to wait on hold for a long time. Ask if it is possible to change your booking and ask if a bulkhead seat is available. Those are at the front of the cabin and some airlines have bassinets. Ideally, at least one of you should be in one of those seats. If that doesn’t work, ask if the airline can change your seats on the phone before check in. The airlines do have the ability to do this but may not want to.
Next, check in early. Online if possible. Some countries may have restrictions on checking in online with a baby so you might not be able to. But if you can, check seating allocations again then. They do change.
If you can’t check in online, get to the airport early. Smile at the check in agent at the desk. Ask nicely. Laugh at their jokes. Ask if they can seat you together.
If that doesn’t work, ask again at the gate.
If that doesn’t work, ask cabin crew when boarding.
If that doesn’t work, ask the person in a middle seat next to you/your husband if they are willing to switch. Offer them the best seat that you or your husband have (window or aisle is better than a middle seat). Accept no for answer if that is what they say. Consider offering cash.
Switch baby between parents a couple of times during the flight whether you are seated next to each other or not. Baby will enjoy a change of scenery. Parent will enjoy the break.