I always feel tiered what can i do to improve this? i also have a 19 month old to run around after

Sleep!: Obvious-- but are you sleeping enough? Most people need 7-8 hours every night; some even more. If sleep is interrupted (by crying kids) you need even more. Consider whether you are depressed; that can present as fatigue. Get adult stimulation and fresh air every day; exercise if at all possible, or at least a daily walk. Those early years are tough; it gets better!

Always sleep: Rule of thumb, if the child is asleep, you should be asleep. Yes, i know that when the child is asleep is a "good time" to get all those other things done, but you need the sleep.

Several things: Sleep is very important. Low carbohydrate high fat high protein diet is very important for you and the child. Frequent snacking to avoid hypoglycemia. Hide your cell phone to decrease stress and check it only periodically. Be checked for post partum hypothyroidism. More common than people think.