Several months back, a Priest I am acquainted with passed onto me a book entitled “To Save a Thousand Souls,” by Fr. Brett A. Brannen.
Being occupied by study at present, I’ve not had the chance to really read it. However, one thing noted in this text is that the first vocation of every person is to lead a life of holiness. That is the first step, and one we must all accomplish in order to be in-tune with God, and His will for us.
As your spirituality grows (even if it’s one step forward, two steps back like me), you can better determine what God’s plan is. The important thing to do is NOT focus on what you want, or what makes you happy here and now.
Emotions are only temporary, really. The typical example of a kid earnestly pestering his mother about the latest toy, who gives in, only for the kid to loose interest after a few days is a prime example. Don’t obsess over particular pathways or lifestyles.
If you do not feel called to marriage or to the religious life, fear not. Remember the first vocation of each and every person is to lead a life of holiness - that is, living out the Gospel, acting in accordance with the Commandments, and so on.
This does lead (somewhat) into the “third vocation,” which is hotly debated. If you are not called to marriage or religious life, then you are to be celibate and chaste. Being single gives other challenges, like not always ‘doing whatever you want because you can,’ but instead trying to use your energy for the good of others or your own spiritual growth.
My hope is that this explanation helps.
Do seek out the guidance of a good spiritual director and/or your Parish Priest, or another Priest you know if you have some sort of preference.
Try and attend some retreats if you can at all. Okay, maybe you don’t want to be in a religious order, but the reflection time and the speaker(s) at these events can help clarify your thoughts. I regularly attend Reflection Weekends offered by a religious order operating/serving where I live, and find the time beneficial for strengthening my spirituality and disconnecting for a while.
As for the discussion on ADHD and Autism, how’s about not discussing this on an open forum. No one is qualified to make that call. The OP needs to look into this themselves if they have a concern.
Finally, concerning the discussion of nicotine, do remember everyone that the Church Herself stipulates it is acceptable PROVIDED any usage is done in temperance, much the same as with Alcohol. Both can be damaging and both can become habitual. My suggestion would be to be mindful that you don’t accidentally lead yourself into an addiction.
Having a drink every now and then is acceptable, but not constantly each day. The same with this.
I do stuff like that sometimes, too. To paraphrase St. Augustine, I sometimes say, “God, give me charity, but not yet…” 
(we are similar in age, after all).