Nevertheless, I never could consistently have real self-control.
The Hinayana Buddhists have a Dharma called the Contemplation of the Impure which is very effective at eliminating greed and desire. You do not need to be vegetarian, and can eat onion and garlic. Eventually, you will be able to maintain the Precepts and attain Arhatship.
Still, Mahayana has many more dharma doors to deal with greed and desire. In particular, the Shurangama Mantra is most effective at eliminating sexual desire. However, it is highly advisable to be vegetarian and avoid eating the five pungent plants in order to maximize its effectiveness. You may realize enlightenment with this dharma door.
You should maintain the Shurangama Mantra. In time, your desires will lessen and you will naturally be more inclined to maintain precepts, become vegetarian and with time, you will enjoy keeping the precepts.
The important thing is to find a competent good knowing adviser who can transmit to you. The Mahayana Dharmas which have stricter requirements, tend to produce more significant and desirable results.