Congrats on the baby. I'm happy for you.
I think we discussed this before but for me I detect unseen things the most when I am low vibrational energy and/or exhausted & run down. And as a newborn mother I'm sure you are very run down & are still adapting to your new baby. So if you're like me you're probably attracting ghosts/negs or feeling them come closer in your current state. My observation is that when we are balance or high vibration, they leave us alone as they don't like that energy. But when are depressed or exhausted, they really like that energy and draw closer to experience the energy or attach. I'm sure you are very excited for your new life with your baby. But from my perspective, you're probably tired on a level you've never seen before. And I believe in your other post you said you are in a new home. That means you're entering a new space where things may be there already.
As to your boyfriend's comment that they seem harmless, I don't agree with that when it comes to an empath. If they are hanging around they are draining you even if they don't seem threatening. Remember, they don't produce their own energy. They have to capture and steal it from humans who make it. And empath energy is like the best of the best to them.
Since you can't sage with the baby, I would suggest trying putting your feet in a warm bucket of salt water daily for 15-20 minutes. Put on some relaxing music and let the salt do it's work to help you rebalance your energy. Usually a full body bath tub salt soak is the best for rebalancing. But if you're limited on time, the foot salt soak is a nice short cut that still helps.