Georgina,
If you want him to sleep in his own bed, and in his own room, then you're laying next to him until he falls asleep is NOT the answer. He has to learn to be comfortable being alone in order to do that....your staying with him until he falls asleep isn't any better for him than your putting him in bed with you!
Spend some quality time with him before bed every night. Read him a story or just talk to him until he gets sleepy, and then leave the room, and don't go back in, even if he cries. Also, leaving a night light on, or your hall light and opening his door slightly may help.
At 17 months, I wouldn't go with a toddler bed just yet, especially if he won't go to sleep on his own in his crib. If you go that route too quickly, you'll not only have to worry about whether or not he's in his bed, but also whether or not he's in his room, once you retire for the night.
This is just a phase that they all go through, and forcing them to make their peace with it on their own is the best thing for them, even if they do get upset about it. How you handle this now will have a direct effect on his sleeping habits later in life, so try to stick to what YOU want him to do, and not give in just because he cries!