Lack of sleep. To and any solution?

I am 31, n mother to a 3 year old daughter. For around an year, I am facing this problem of not getting proper sleep. I may be very tired or just fine, or I might not have slept well the previous night as well but I don't get sleep. My sleep cycle has reduced to around 4 hours of sleep per day. A good night's sleep for me is 6 hours at a stretch, which I hardly get any. I have followed various advises from various people, like switching off my phone while sleeping, taking a bath before sleep, Completely giving up any rest in the afternoon, Doing a physical activity like talking a long walk These ways gave me sleep once or twice but  hasn't really worked till now. I have recently joined work too since a week. So my mental n physical work load is increased, but my sleep remains affected. I feel very drowsy at night n too worked up. But don't get sleep. I get frequent headaches due to sleeplessness, dark circles etc. I want to know which doctor should i refer to and any solution