I'm under a lot of stress.

under Preposition

— In the same place as another thing, but lower. They ate under the trees. — In the control of. He was under the leader of the organization. — In the middle of a process; experiencing. The idea is under the committee's judgement (judging).

a Determinative

— A is used when the following word could be any of a certain type. Compare "A book I saw on the shelf" and "The book I gave you yesterday".

a Noun

— A is the first letter of the alphabet. The letter "a" comes before "b". — In some schools, an A is a very high grade. Ron got an A on his earth science test.

lot Noun

— A lot of something is a large amount of it. I have a lot of things to say. He caused lots of trouble. — To a large degree Running is lots more fun when the weather is cool. — Often He used to come here a lot, but he doesn't anymore. — A lot is a piece of land, usually small. They are constructing a building on this lot.

of Preposition

— Made using. It is a house of cards.

stress Noun

— Stress is emotional pressure that makes you worry because things are not going well. Death is a time of great stress for family and friends. Plants under stress from lack of water or disease are the most likely to attract problem insects. — Stress is physical pressure that gradually can cause things to break Sitting puts an unnatural stress on the back and shortens the neck. — Stress is extra attention or importance that you put on something. Psychology has put a lot of stress on the childhood roots of adult problems. — Stress is extra loudness that you use in a word or in music. Put more stress on the first syllable of the word.

stress Verb

— If you stress something, you say that it is very important. I have repeatedly stressed the importance of hard work, but luck is also helpful. — If you stress a word, part of a word, or a note in music, you make it louder than other words or notes.