This is determined by a whole group of different aspects to be perceived by you.
1. The way he /she looks at you and what his eyes are telling during the time period of eye contact. Are he/she comforting? Are they open or blocked off? Do they sparkle? Is there a warming or cold feeling when stating into them, is there eye contact involved and how long it is held
2. Next would be communication, how does he/she speak to you and in which tones and when emphasized. What topics does the person discuss with you? Do they provide eye contact while talking to you or look around, do they speak to you different then other women /men, does he/she comment and compliment you or judge your decisions/opinions, how open is he/she with sharing his feelings and emotions.
3. Bodily language says a lot. The positioning of the body accounts to this, arm movements, are they moving fast or slow/ gracefully or abrupt, do the feet face you when in a standing position, do they stand tall and confidently when surrounded by you or do they slouch and look disoriented.
4. Vibes and feelings you get from that special person. When accompanied with them do you feel like a king/queen or do you feel like your an annoyance or bothering them/in their way, does your heart feel heavy or light around them, are you calm in he/she company or do you suffer with anxiety and tenseness, do you sense when their in the same room as you or are you numbed from that person's energy, do you think and act sometimes in actions similar to how your partner does at times or are you two completely different minds and never think the same thing.
5. Actions - does he-she like suprising you with either a gift, a nice outing, or something in anyway relates to what you like or enjoy doing? Are they choosing correct gestures or doings things in which you have interests in or are they focusing on what they like. Does he/she hold your hand in public or give you attention when you desire, does it revolve around sex or does he appreciates the basic old school company of your personality, what does he/she compliment you on? ; Appearances or characteristics/personality of you. Does he go out of his/her way when your in time of need or does it feel empty and neglected.
6. Loyality- has he/she cheated on you now or past tense? If so the relationship won't work out at needless to say.
Honesty- is he/she open and honest and willing to talk, discuss and express anything to you or is there uncertainty, avoidance, and breaks between his/her sentence wordings.
Respect- does he/she listen to your topics communicated with him/her and appreciate your comments even if disagreement is on their side or do they cut you off/ talk over the top of you/ try to convince you differ or argue over it.
Trust- Would you let your partner be out of your sight for a week in Vegas... Haha
Why not? You trust him/her yes?
Do you think about your partner while their not in the same surroundings your present in? What sort of things are you thinking about , are you running through your head that he/she might cheat on you. Can you talk to him/her about everything and anything and know that they won't tell a soul.
There's are a couple distinctive factors to take into consideration when wondering if that individual is the perfect person for you and whether they love you. Ask yourself some of those questions and your own mind/heart and soul will give you the answers you need to know. Confidence in one's love doesn't need to be questioned it is felt . If the doubt or understatement is there.. I'd reconsider personally.