I feel like I can write a book on this topic because of all the research and trips to the doctor. We've had the same problem with our daughter.
Some days our tricks would work and some days they would not. The days that did my husband and I were eternally greatful.
Here's some things we did:
1. Change her diaper, give her a sippy of milk, give her a kiss and tell her it is too early to wake up, she is still tired, and that she HAS TO go back to sleep. We'd turn off the monitor and not go into her room until 5:30 or 6 am.
2. Put a brighter light in her room. She literally sleeps with a lamp now and I swear if we would have done that earlier she would have slept through the night. 14 months is when their imaginations go wild, and maybe your son is scared. Night lights cast scary shadows, but a soft, dim/bright enough light helped us.
3. Experts say let them cry it out and do not go in at all. I HATE this theory. The times I tried it my daughter would cry so hard she's make herself thrown up. I'd go up to her room feeling like the worst mother in the world. Then I'd have to change her sheets and make more of a production out of her issue than entirely necessary. I mention it because it DOES work for some toddlers.
4.Sleep on the floor in his room when he wakes up too early and you are at wits end. This shows him that you are there, but it's still time to sleep. He may zonk, he may not, but at least you can get in another hour of sleep and send a message to your son it's time for him to sleep too, and this is how.
5. My doctor also recommends giving a toddler a piece of fruit or a cracker, and then putting your child back down right away. Your son could be going through a growth spurt and may be hungry.
6. Stop rocking him to sleep. Leave the room while he is on the verge of falling aleep. It is proven that toddlers who fall asleep by rocking do not know how to put themselves back to sleep on their own. Instead, focus on a bedtime routine. An easy one is a long warm bath, dim lights, and a few stories. He will learn to associate bedtime with these activities instead of rocking. Plus it will empower him because he can go to sleep on his own, and put himself back to sleep. I believe this helps in early development of good self-esteem. If it does not work for you though, do not fret!
I've read all the other responses and I am happy to hear those things worked for the other moms. I've also tried just one method, but it did not work for our daughter. Remember that some toddlers require a multitude of methods because their issues change on a daily basis. Your son may not be sleeping because he's constipated, or he's scared, or he's thirsty, he's testing his boundaries with your attention, or he just wants to see his momma. Whatever it is, it is going to require a different action, or it may not! Consistency has a time and place, be willing to bend the rules and explore different ways.
Best wishes, hang in there, good luck! There's no one answer for such a complicated issue, but hopefully some of these work for you and your family!
K. F.