3.5 Month Old Development

I have a few concerns about my 3.5 month old development. He doesn't follow objects yet. He also doesn't turn towards my voice or my husbands, but I know he can hear because he startles. My husband and I will talk to him and he doesn't look at us. Occasionally he will look at us and make eye contact and smile. He doesn't swipe at objects and he doesn't push off with his legs on a firm surface. He coos and smiles though when he makes direct eye contact. I just can't seem to get his attention.

Is this okay? What do you suggest I do now?