There is no difference between Kundalini and sexual energy. In Yoga, sexual energy is called Shakti, and sometimes is personificated as Goddess. This energy is motivational force, she is the reason why we are live. The Life itself is manifestation of Kundalini or sexual energy in this or that form.
Human body is composed from Masculine and Feminine principle. Right side of the body is Masculine, and left is Feminine. Masculine and Feminine principle meets in the middle line, in the central energetic channel. On the Sanskrit, this central line is called Sushumna. This line is in the middle of the body, in the "heart of body".
When sexual energy is active from diaphragm to the below, we experience this energy as sexuality: sexual appetite, sexual sensitivity, sexual thoughts. When sexual energy is active from diaphragm to the eyebrows above, in central energetic channel, we experience this energy like Divine Love, Love of the Heart or Love of Surrender. When sexual energy operate in central energetic channel, in cupola of the head, we experience this energy like Divinity.
In all three cases, it is about the same sexual energy, but the areas of manifestation are different. There is no difference in energy. Energy is energy, Shakti or sexual energy.
Sexual energy is central Life energy, and your true being, your true nature is in the center. That is the reason why you cannot push your sexuality on the side, and live your Life. That is impossible. If you do like that, you will end up with false personality, your Life will be false, and it will seems to you that everything is fraud (false), and you will be right. Everything will be artificial, false, rattle, unrealistic, and it doesn't matter what is happening, you will never be really satisfied, because that core, who you really are, is not satisfied. From this reason, if you want something to do with your Life, you must deal with the matter of sexuality.
There are two basic paths for transformation of sexual energy, and they are sexual restrain (right tantric path), and sexual indulgence (left tantric path).