How much should I really eat? (Calories)

So I'm 18 years old and I'm 5'3 weighing in about 150 pounds. Since it's summer I usually wake up around 3pm and eat right away which includes rice and vegetables or meat. Around 6-7pm I eat something light like a bowl of cereal and a milkshake (banana with milk and ice). Around 11pm I begin my work out that lasts about 1 hour and by the end of it I'm definitely sweating my butt off haha. I really try not to eat afterwards because then I feel guilty. I understand I'm not eating as much as I should but it's just really hard because I'm trying to lose all this weight and by eating I feel extremely guilty. Any tips? Anything would really help! Thanks in advance.