Strength is very strongly correlated to muscle size, it's just a slow process. Keep getting stronger and you'll get bigger.
You also need surplus calories to optimally build muscle... so once you're lean, you might want to add a little extra protein and post workout carbs (taters, fruit, rice) to up your calories and maximize recovery.
Lastly, doing a combination of strength work and higher volume training is generally regarded as best when hypertrophy is your goal. Give this article a read for a bit more on muscle growth if you're interested in the science behind it!